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Strange numbers

From Rosetta Code
Strange numbers is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
Definition

n   is a   strange number   (expressed in base ten)   if every adjacent decimal digit differs from its neighbour by a prime number.


Task

Show all strange numbers for   100   <   n   <   500


Stretch goal

Show the number of 10-digit strange numbers that begin with 1

11l[edit]

Translation of: Python
F is_strange(n)
V xs = String(n).map(c -> Int(c))
R all(zip(xs, xs[1..]).map((a, b) -> abs(a - b) C (2, 3, 5, 7)))
 
V xs = (100..500).filter(n -> is_strange(n))
print("\nStrange numbers in range [100..500]\n")
print(‘(Total: ’String(xs.len)")\n")
L(el) xs
print(el, end' ‘ ’)
I L.index % 10 == 9
print()
Output:
Strange numbers in range [100..500]

(Total: 87)

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497

ALGOL W[edit]

begin % find "strange numbers" - numbers where digits differ from the next %
 % by a prime  %
 % returns true if n is strange, false otherwise  %
logical procedure isStrange( integer value n ) ;
begin
integer rest;
rest  := abs( n );
if rest < 10 then false
else begin
logical strange;
integer d0;
strange := true;
d0  := rest rem 10;
rest  := rest div 10;
while strange and rest > 0 do begin
integer d1, diff;
d1  := rest rem 10;
rest  := rest div 10;
diff  := abs( d1 - d0 );
strange := diff = 2 or diff = 3 or diff = 5 or diff = 7;
d0  := d1
end while_strange_and_rest_gt_0 ;
strange
end if_rest_lt_10__
end isStrange ;
 % test the isStrange procedure on values 100-499  %
begin
integer strangeCount;
strangeCount := 0;
for n := 100 until 499 do begin;
if isStrange( n ) then begin
strangeCount := strangeCount + 1;
if strangeCount rem 20 = 1
then write( i_w := 4, s_w := 0, n )
else writeon( i_w := 4, s_w := 0, n )
end if_isStrange_n
end for_n
end
end.
Output:
 130 131 135 136 138 141 142 146 147 149 161 163 164 168 169 181 183 185 186 202
 203 205 207 241 242 246 247 249 250 252 253 257 258 270 272 274 275 279 292 294
 296 297 302 303 305 307 313 314 316 318 350 352 353 357 358 361 363 364 368 369
 381 383 385 386 413 414 416 418 420 424 425 427 429 461 463 464 468 469 470 472
 474 475 479 492 494 496 497

APL[edit]

(⊢(/⍨)(∧/2 3 5 7∊⍨2+/⍎¨∘⍕)¨) 100+⍳400
Output:
111 112 114 116 120 121 123 125 141 143 161 202 203 205 207 211 212 214 216 230 232 234 250 252 302 303 305 307 320 321
      323 325 341 343 411 412 414 416 430 432 434

AppleScript[edit]

--------------------- STRANGE NUMBERS --------------------
 
-- isStrange :: Int -> Bool
on isStrange(n)
set ds to digits(n)
 
script sumIsSmallPrime
on |λ|(a, b)
{2, 3, 5, 7} contains abs(a - b)
end |λ|
end script
 
zipWith(sumIsSmallPrime, ds, rest of ds) ¬
does not contain false
end isStrange
 
 
--------------------------- TEST -------------------------
on run
set xs to filter(isStrange, enumFromTo(100, 500))
 
intercalate("\n\n", ¬
{"Strange numbers found in range [100..500]", ¬
"Full list:", ¬
("(total " & (length of xs) as string) & ")", ¬
unlines(map(unwords, chunksOf(10, map(str, xs))))})
end run
 
 
------------------------- GENERIC ------------------------
 
-- abs :: Num -> Num
on abs(x)
-- Absolute value.
if 0 > x then
-x
else
x
end if
end abs
 
 
-- chunksOf :: Int -> [a] -> [[a]]
on chunksOf(k, xs)
script
on go(ys)
set ab to splitAt(k, ys)
set a to item 1 of ab
if {} ≠ a then
{a} & go(item 2 of ab)
else
a
end if
end go
end script
result's go(xs)
end chunksOf
 
 
-- digits :: Int -> [Int]
on digits(n)
script go
on |λ|(x)
x as integer
end |λ|
end script
map(go, characters of (n as string))
end digits
 
 
-- enumFromTo :: Int -> Int -> [Int]
on enumFromTo(m, n)
if m ≤ n then
set lst to {}
repeat with i from m to n
set end of lst to i
end repeat
lst
else
{}
end if
end enumFromTo
 
 
-- intercalate :: String -> [String] -> String
on intercalate(delim, xs)
set {dlm, my text item delimiters} to ¬
{my text item delimiters, delim}
set s to xs as text
set my text item delimiters to dlm
s
end intercalate
 
 
-- filter :: (a -> Bool) -> [a] -> [a]
on filter(p, xs)
tell mReturn(p)
set lst to {}
set lng to length of xs
repeat with i from 1 to lng
set v to item i of xs
if |λ|(v, i, xs) then set end of lst to v
end repeat
if {text, string} contains class of xs then
lst as text
else
lst
end if
end tell
end filter
 
 
-- mReturn :: First-class m => (a -> b) -> m (a -> b)
on mReturn(f)
-- 2nd class handler function lifted into 1st class script wrapper.
if script is class of f then
f
else
script
property |λ| : f
end script
end if
end mReturn
 
 
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
-- The list obtained by applying f
-- to each element of xs.
tell mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to |λ|(item i of xs, i, xs)
end repeat
return lst
end tell
end map
 
 
-- min :: Ord a => a -> a -> a
on min(x, y)
if y < x then
y
else
x
end if
end min
 
 
-- splitAt :: Int -> [a] -> ([a], [a])
on splitAt(n, xs)
if n > 0 and n < length of xs then
if class of xs is text then
{items 1 thru n of xs as text, ¬
items (n + 1) thru -1 of xs as text}
else
{items 1 thru n of xs, items (n + 1) thru -1 of xs}
end if
else
if n < 1 then
{{}, xs}
else
{xs, {}}
end if
end if
end splitAt
 
 
-- str :: a -> String
on str(x)
x as string
end str
 
 
-- unlines :: [String] -> String
on unlines(xs)
-- A single string formed by the intercalation
-- of a list of strings with the newline character.
set {dlm, my text item delimiters} to ¬
{my text item delimiters, linefeed}
set s to xs as text
set my text item delimiters to dlm
s
end unlines
 
 
-- unwords :: [String] -> String
on unwords(xs)
set {dlm, my text item delimiters} to ¬
{my text item delimiters, space}
set s to xs as text
set my text item delimiters to dlm
return s
end unwords
 
 
-- zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
on zipWith(f, xs, ys)
set lng to min(length of xs, length of ys)
set lst to {}
if 1 > lng then
return {}
else
tell mReturn(f)
repeat with i from 1 to lng
set end of lst to |λ|(item i of xs, item i of ys)
end repeat
return lst
end tell
end if
end zipWith
Output:
Strange numbers found in range [100..500]

Full list:

(total 87)

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497

AWK[edit]

 
# syntax: GAWK -f STRANGE_NUMBERS.AWK
BEGIN {
start = 100
stop = 500
for (i=start; i<=stop; i++) {
flag = 1
for (j=1; j<length(i); j++) {
if (!(is_prime(abs(substr(i,j,1)-substr(i,j+1,1))))) {
flag = 0
break
}
}
if (flag == 1) {
printf("%d%1s",i,++count%10?"":"\n")
}
}
printf("\nStrange numbers %d-%d: %d\n",start,stop,count)
exit(0)
}
function is_prime(x, i) {
if (x <= 1) {
return(0)
}
for (i=2; i<=int(sqrt(x)); i++) {
if (x % i == 0) {
return(0)
}
}
return(1)
}
function abs(x) { if (x >= 0) { return x } else { return -x } }
 
Output:
130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497
Strange numbers 100-500: 87

BASIC[edit]

10 DEFINT I,J,K: DEFSTR S
20 FOR I=100 TO 500
30 S=STR$(I)
40 FOR J=2 TO LEN(S)-1
50 K=ABS(VAL(MID$(S,J,1))-VAL(MID$(S,J+1,1)))
60 IF K<>2 AND K<>3 AND K<>5 AND K<>7 THEN 90
70 NEXT J
80 PRINT I,
90 NEXT I
Output:
 130           131           135           136           138
 141           142           146           147           149
 161           163           164           168           169
 181           183           185           186           202
 203           205           207           241           242
 246           247           249           250           252
 253           257           258           270           272
 274           275           279           292           294
 296           297           302           303           305
 307           313           314           316           318
 350           352           353           357           358
 361           363           364           368           369
 381           383           385           386           413
 414           416           418           420           424
 425           427           429           461           463
 464           468           469           470           472
 474           475           479           492           494
 496           497

BCPL[edit]

get "libhdr"
 
let dgtprime(x) = x=2 | x=3 | x=5 | x=7
let strange(x) =
x<10 -> true,
dgtprime(abs(x rem 10 - (x/10) rem 10)) & strange(x/10)
 
let start() be
$( let col = 0
for i=100 to 500 do
if strange(i) then
$( writed(i, 4)
col := col + 1
if col rem 10 = 0 then wrch('*N')
$)
wrch('*N')
$)
Output:
 130 131 135 136 138 141 142 146 147 149
 161 163 164 168 169 181 183 185 186 202
 203 205 207 241 242 246 247 249 250 252
 253 257 258 270 272 274 275 279 292 294
 296 297 302 303 305 307 313 314 316 318
 350 352 353 357 358 361 363 364 368 369
 381 383 385 386 413 414 416 418 420 424
 425 427 429 461 463 464 468 469 470 472
 474 475 479 492 494 496 497

BQN[edit]

↑‿10⥊((∧´(|¯1↓«-⊢)∊⟨2,3,5,7⟩˙)○•Fmt)¨⊸/100+↕400
Output:

The unused positions in the table are filled with 0s, because that's the behaviour of ↑‿10⥊, and writing custom tabulation code would take much more code than the actual task.

┌─                                         
╵ 130 131 135 136 138 141 142 146 147 149  
  161 163 164 168 169 181 183 185 186 202  
  203 205 207 241 242 246 247 249 250 252  
  253 257 258 270 272 274 275 279 292 294  
  296 297 302 303 305 307 313 314 316 318  
  350 352 353 357 358 361 363 364 368 369  
  381 383 385 386 413 414 416 418 420 424  
  425 427 429 461 463 464 468 469 470 472  
  474 475 479 492 494 496 497   0   0   0  
                                          ┘

C[edit]

Translation of: Go
#include <stdbool.h>
#include <stdio.h>
 
bool isPrime(int n) {
if (n < 0) {
n = -n;
}
return n == 2 || n == 3 || n == 5 || n == 7;
}
 
int main() {
int count = 0;
int i, j;
int d[3];
int dptr;
 
printf("Strange numbers in the open interval (100, 500) are:\n");
for (i = 101; i < 500; i++) {
dptr = 0;
j = i;
while (j > 0) {
d[dptr++] = j % 10;
j /= 10;
}
if (isPrime(d[0] - d[1]) && isPrime(d[1] - d[2])) {
printf("%d ", i);
count++;
if (count % 10 == 0) {
printf("\n");
}
}
}
if (count % 10 != 0) {
printf("\n");
}
printf("\n%d strange numbers in all.\n", count);
 
return 0;
}
Output:
Strange numbers in the open interval (100, 500) are:
130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497

87 strange numbers in all.

C++[edit]

Translation of: Java
#include <algorithm>
#include <iostream>
#include <vector>
 
std::vector<int> digits(int n) {
std::vector<int> result;
while (n > 0) {
auto rem = n % 10;
result.push_back(rem);
n /= 10;
}
std::reverse(result.begin(), result.end());
return result;
}
 
bool is_strange(int n) {
auto test = [](int a, int b) {
auto v = std::abs(a - b);
return v == 2 || v == 3 || v == 5 || v == 7;
};
 
auto xs = digits(n);
for (size_t i = 1; i < xs.size(); i++) {
if (!test(xs[i - 1], xs[i])) {
return false;
}
}
return true;
}
 
int main() {
std::vector<int> xs;
for (int i = 100; i <= 500; i++) {
if (is_strange(i)) {
xs.push_back(i);
}
}
 
std::cout << "Strange numbers in range [100..500]\n";
std::cout << "(Total: " << xs.size() << ")\n\n";
 
for (size_t i = 0; i < xs.size(); i++) {
std::cout << xs[i];
if ((i + 1) % 10 == 0) {
std::cout << '\n';
} else {
std::cout << ' ';
}
}
 
return 0;
}
Output:
Strange numbers in range [100..500]
(Total: 87)

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497

COBOL[edit]

        IDENTIFICATION DIVISION.
PROGRAM-ID. STRANGE-NUMBERS.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01 COMPUTATION.
02 NUM PIC 999.
02 DIGITS REDEFINES NUM PIC 9 OCCURS 3 TIMES.
02 DIGIT-PRIME PIC 9.
88 PRIME VALUES 2 3 5 7.
02 CUR-DIGIT PIC 9.
01 OUTPUT-FORMAT.
02 N-OUT PIC ZZ9.
PROCEDURE DIVISION.
BEGIN.
PERFORM STRANGE-TEST
VARYING NUM FROM 100 BY 1
UNTIL NUM IS GREATER THAN 500.
STOP RUN.
 
STRANGE-TEST SECTION.
BEGIN.
SET CUR-DIGIT TO 1.
STEP.
IF DIGITS(CUR-DIGIT) IS LESS THAN DIGITS(CUR-DIGIT + 1)
SUBTRACT DIGITS(CUR-DIGIT + 1) FROM DIGITS(CUR-DIGIT)
GIVING DIGIT-PRIME
ELSE
SUBTRACT DIGITS(CUR-DIGIT) FROM DIGITS(CUR-DIGIT + 1)
GIVING DIGIT-PRIME.
IF PRIME NEXT SENTENCE ELSE GO TO DONE.
ADD 1 TO CUR-DIGIT.
IF CUR-DIGIT IS LESS THAN 3 GO TO STEP.
MOVE NUM TO N-OUT.
DISPLAY N-OUT.
DONE. EXIT.
Output:
130
131
135
136
138
141
142
146
147
149
161
163
164
168
169
181
183
185
186
202
203
205
207
241
242
246
247
249
250
252
253
257
258
270
272
274
275
279
292
294
296
297
302
303
305
307
313
314
316
318
350
352
353
357
358
361
363
364
368
369
381
383
385
386
413
414
416
418
420
424
425
427
429
461
463
464
468
469
470
472
474
475
479
492
494
496
497

F#[edit]

 
// Strange numbers. Nigel Galloway: February 25th., 2021
let N=Array.init 10(fun n->[2;3;5;7]|>List.collect(fun g->[n+g;n-g])|>List.filter((<) -1)|>List.filter((>)10))
[1..4]|>List.collect(fun g->N.[g]|>List.map(fun n->g*10+n%10))|>List.collect(fun n->N.[n%10]|>List.map(fun g->n*10+g%10))|>List.iter(printf "%d "); printfn ""
 
Output:
130 131 135 136 138 141 142 146 147 149 161 163 164 168 169 180 181 183 185 186 202 203 205 207 241 242 246 247 249 250 252 253 257 258 270 272 274 275 279 292 294 296 297 302 303 305 307 313 314 316 318 350 352 353 357 358 361 363 364 368 369 380 381 383 385 386 413 414 416 418 420 424 425 427 429 461 463 464 468 469 470 472 474 475 479 492 494 496 497

Factor[edit]

Identifying and filtering[edit]

Works with: Factor version 0.99 2020-08-14
USING: grouping io kernel math.ranges math.statistics
math.text.utils math.vectors prettyprint sequences ;
 
: strange? ( n -- ? )
1 digit-groups differences vabs
[ { 2 3 5 7 } member? ] all? ;
 
"Strange numbers in (100, 500):" print nl
100 500 (a,b) [ strange? ] filter dup
10 group [ [ pprint bl ] each nl ] each nl
length pprint " strange numbers found." print
Output:
Strange numbers in (100, 500):

130 131 135 136 138 141 142 146 147 149 
161 163 164 168 169 181 183 185 186 202 
203 205 207 241 242 246 247 249 250 252 
253 257 258 270 272 274 275 279 292 294 
296 297 302 303 305 307 313 314 316 318 
350 352 353 357 358 361 363 364 368 369 
381 383 385 386 413 414 416 418 420 424 
425 427 429 461 463 464 468 469 470 472 
474 475 479 492 494 496 497 

87 strange numbers found.

Generating[edit]

Since we know the next possible digits based on the current last digit, we can construct strange numbers with a backtracking algorithm.

Works with: Factor version 0.99 2020-08-14
USING: backtrack compiler.tree.propagation.call-effect
formatting io kernel sequences sequences.generalizations
tools.memory.private tools.time ;
 
: d ( digit -- digit next-digit )
dup {
{ 2 3 5 7 }  ! from 0 we can get to these digits
{ 3 4 6 8 }  ! from 1 we can get to these
{ 0 4 5 7 9 }  ! etc...
{ 0 1 5 6 8 }
{ 1 2 6 7 9 }
{ 0 2 3 7 8 }
{ 1 3 4 8 9 }
{ 0 2 4 5 9 }
{ 1 3 5 6 }
{ 2 4 6 7 }
} nth amb-lazy ;
 
[ [ 1 d d d d d d d d d 10 narray ] bag-of ] time
 
dup length commas write
" 10-digit strange numbers beginning with 1:" print
[ first2 ] [ last2 ] bi "%u\n%u\n...\n%u\n%u\n" printf
Output:
Running time: 1.904245898 seconds

853,423 10-digit strange numbers beginning with 1:
{ 1 3 0 2 0 2 0 2 0 2 }
{ 1 3 0 2 0 2 0 2 0 3 }
...
{ 1 8 6 9 7 9 7 9 7 5 }
{ 1 8 6 9 7 9 7 9 7 9 }

FreeBASIC[edit]

function is_strange( n as ulongint ) as boolean
dim as uinteger d, ld, a
if n<10 then return true 'arbitrary, but makes the recursion easier
d = n mod 10
ld = (n mod 100) \ 10
a = abs(d - ld)
if a = 2 or a = 3 or a = 5 or a = 7 then return is_strange(n\10) else return false
end function
 
print "Strange numbers between 100 and 500"
for n as uinteger = 101 to 499
if is_strange(n) then print n;" ";
next n
print : print
 
dim as integer c = 0
for n as ulongint = 1000000000 to 1999999999
if is_strange(n) then c+=1
next n
print using "There are ####### 10-digit strange numbers beginning with 1.";c
Output:

Strange numbers between 100 and 500 130 131 135 136 138 141 142 146 147 149 161 163 164 168 169 181 183 185 186 202 203 205 207 241 242 246 247 249 250 252 253 257 258 270 272 274 275 279 292 294 296 297 302 303 305 307 313 314 316 318 350 352 353 357 358 361 363 364 368 369 381 383 385 386 413 414 416 418 420 424 425 427 429 461 463 464 468 469 470 472 474 475 479 492 494 496 497

There are 853423 10-digit strange numbers beginning with 1.

Forth[edit]

\ tests whether n is prime for 0 <= n < 10
: prime? ( n -- ? )
1 swap lshift 0xac and 0<> ;
 
: strange? ( n -- ? )
dup 10 < if drop false exit then
10 /mod swap >r
begin
dup 0 >
while
10 /mod swap
dup r> - abs
prime? invert if 2drop false exit then
>r
repeat
drop rdrop true ;
 
: main
0
500 101 do
i strange? if
i .
1+
dup 10 mod 0= if cr then else
then
loop
cr
drop ;
 
main
bye
Output:
130 131 135 136 138 141 142 146 147 149 
161 163 164 168 169 181 183 185 186 202 
203 205 207 241 242 246 247 249 250 252 
253 257 258 270 272 274 275 279 292 294 
296 297 302 303 305 307 313 314 316 318 
350 352 353 357 358 361 363 364 368 369 
381 383 385 386 413 414 416 418 420 424 
425 427 429 461 463 464 468 469 470 472 
474 475 479 492 494 496 497 

Go[edit]

Basic task[edit]

Translation of: Wren
package main
 
import "fmt"
 
func isPrime(n int) bool {
if n < 0 {
n = -n
}
return n == 2 || n == 3 || n == 5 || n == 7
}
 
func main() {
count := 0
var d []int
fmt.Println("Strange numbers in the open interval (100, 500) are:\n")
for i := 101; i < 500; i++ {
d = d[:0]
j := i
for j > 0 {
d = append(d, j%10)
j /= 10
}
if isPrime(d[0]-d[1]) && isPrime(d[1]-d[2]) {
fmt.Printf("%d ", i)
count++
if count%10 == 0 {
fmt.Println()
}
}
}
if count%10 != 0 {
fmt.Println()
}
fmt.Printf("\n%d strange numbers in all.\n", count)
}
Output:
Strange numbers in the open interval (100, 500) are:

130 131 135 136 138 141 142 146 147 149 
161 163 164 168 169 181 183 185 186 202 
203 205 207 241 242 246 247 249 250 252 
253 257 258 270 272 274 275 279 292 294 
296 297 302 303 305 307 313 314 316 318 
350 352 353 357 358 361 363 364 368 369 
381 383 385 386 413 414 416 418 420 424 
425 427 429 461 463 464 468 469 470 472 
474 475 479 492 494 496 497 

87 strange numbers in all.

Stretch goal[edit]

Translation of: Julia
package main
 
import "fmt"
 
func main() {
diffs := []int{-7, -5, -3, -2, 2, 3, 5, 7}
possibles := make([][]int, 10)
for i := 0; i < 10; i++ {
possibles[i] = []int{}
for _, d := range diffs {
sum := i + d
if sum >= 0 && sum < 10 {
possibles[i] = append(possibles[i], sum)
}
}
}
 
places := 10
start := 1
strangeOnes := []int{start}
for i := 2; i <= places; i++ {
var newOnes []int
for _, n := range strangeOnes {
for _, nextN := range possibles[n%10] {
newOnes = append(newOnes, n*10+nextN)
}
}
strangeOnes = newOnes
}
fmt.Println("Found", len(strangeOnes), places, "\b-digit strange numbers beginning with", start)
}
Output:
Found 853423 10-digit strange numbers beginning with 1.

Haskell[edit]

import Data.List (intercalate)
import Data.List.Split (chunksOf)
 
--------------------- STRANGE NUMBERS --------------------
 
isStrange :: Int -> Bool
isStrange n =
all
(\(a, b) -> abs (a - b) `elem` [2, 3, 5, 7])
$ (zip <*> tail) (digits n)
 
digits :: Int -> [Int]
digits = fmap (read . return) . show
 
--------------------------- TEST -------------------------
main =
let xs = filter isStrange [100 .. 500]
in (putStrLn . intercalate "\n\n")
[ "Strange numbers found in range [100..500]",
"(total " <> (show . length) xs <> ")",
"Full list:",
unlines
(unwords <$> chunksOf 10 (show <$> xs))
]
Output:
Strange numbers found in range [100..500]

(total 87)

Full list:

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497

Java[edit]

Translation of: Python
import java.util.LinkedList;
import java.util.List;
import java.util.function.BiPredicate;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
 
public class StrangeNumbers {
private static List<Integer> digits(int n) {
var result = new LinkedList<Integer>();
while (n > 0) {
var rem = n % 10;
result.addFirst(rem);
n /= 10;
}
return result;
}
 
private static boolean isStrange(int n) {
BiPredicate<Integer, Integer> test = (a, b) -> {
var abs = Math.abs(a - b);
return abs == 2 || abs == 3 || abs == 5 || abs == 7;
};
 
var xs = digits(n);
for (int i = 1; i < xs.size(); i++) {
if (test.negate().test(xs.get(i - 1), xs.get(i))) {
return false;
}
}
return true;
}
 
public static void main(String[] args) {
var xs = IntStream.rangeClosed(100, 500)
.filter(StrangeNumbers::isStrange)
.boxed()
.collect(Collectors.toList());
 
System.out.println("Strange numbers in range [100..500]");
System.out.printf("(Total: %d)\n\n", xs.size());
 
for (int i = 0; i < xs.size(); i++) {
Integer x = xs.get(i);
System.out.print(x);
 
if ((i + 1) % 10 == 0) {
System.out.println();
} else {
System.out.print(' ');
}
}
}
}
Output:
Strange numbers in range [100..500]
(Total: 87)

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497 

jq[edit]

Works with: jq

Works with gojq, the Go implementation of jq

Filter method[edit]

 
def is_strange:
def digits: tostring | explode | map([.] | implode | tonumber);
digits
| . as $d
| [2, 3, 5, 7] as $primes
| all( range(1; length);
($d[.] - $d[. - 1]) | length | IN( $primes[]));
 
# Pretty-printing
def nwise($n):
def n: if length <= $n then . else .[0:$n] , (.[$n:] | n) end;
n;
 
def lpad($len): tostring | ($len - length) as $l | (" " * $l)[:$l] + .;
 
def task($start; $stop; filter):
"Finding numbers matching $f for open interval \($start), \($stop):\n",
( [range($start; $stop) | select(filter) ]
| nwise(10) | map(lpad(3)) | join(" ") );
 
task(100; 500; is_strange)
 
Output:
 
Finding numbers matching $f for open interval 100, 500:

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497


Generator method[edit]

`lpad` and and `nwise` are as above and so their definitions are not repeated.

 
# input: width
# $start: maximum first digit allowed e.g. 9 for unrestricted
# output: the specified stream of strange numbers
def generate($start):
# The next permissible digit
def nxt: . as $i | range(0;10) | select($i - . | length | IN(2, 3, 5, 7));
 
# input: width
# $first: first digit
# output: an array of $n digits
def gen($first):
. as $n
| if $n == 0 then []
elif $n == 1 then [$first]
else ($n - 1) | gen($first) | . + ((.[-1]|nxt) | [.])
end;
 
gen( range(1; $start+1) );
 
[3 | generate(4) | map(tostring) | join("") | tonumber]
| nwise(10) | map(lpad(3)) | join(" ")
 
Output:

As above, except for the header.

Stretch goal[edit]

Using generate/1 as already defined:

 
def count(s): reduce s as $x (null; .+1);
count(10 | generate(1))
 
Output:
853423

Julia[edit]

Filter method[edit]

isstrange(n::Integer) = (d = digits(n); all(i -> abs(d[i] - d[i + 1]) ∈ [2, 3, 5, 7], 1:length(d)-1))
 
function filter_open_interval(start, stop, f, doprint=true, rowlength=92)
colsize = length(string(stop)) + 1
columns, ncount = rowlength ÷ colsize, 0
println("Finding numbers matching $f for open interval ($start, $stop):\n")
for n in start+1:stop-1
if f(n)
ncount += 1
doprint && print(rpad(n, colsize), ncount % columns == 0 ? "\n" : "")
end
end
println("\n\nThe total found was $ncount\n\n")
end
 
filter_open_interval(100, 500, isstrange)
 
Output:
Finding numbers matching isstrange for open interval (100, 500):

130 131 135 136 138 141 142 146 147 149 161 163 164 168 169 181 183 185 186 202 203 205 207
241 242 246 247 249 250 252 253 257 258 270 272 274 275 279 292 294 296 297 302 303 305 307
313 314 316 318 350 352 353 357 358 361 363 364 368 369 381 383 385 386 413 414 416 418 420
424 425 427 429 461 463 464 468 469 470 472 474 475 479 492 494 496 497

The total found was 87

Generator method[edit]

HT: Factor for the table.

function countstrange(places, fixedstart=1)
possibles = [
[2, 3, 5, 7],
[3, 4, 6, 8],
[0, 4, 5, 7, 9],
[0, 1, 5, 6, 8],
[1, 2, 6, 7, 9],
[0, 2, 3, 7, 8],
[1, 3, 4, 8, 9],
[0, 2, 4, 5, 9],
[1, 3, 5, 6],
[2, 4, 6, 7],
]
strangeones = [fixedstart]
for _ in 2:places
newones = Int[]
for n in strangeones, nextn in possibles[n % 10 + 1]
push!(newones, n * 10 + nextn)
end
strangeones = newones
end
println("Found ", length(strangeones), " $places-digit strange numbers with the most significant digit $fixedstart.\n")
end
 
countstrange(10)
@time countstrange(10)
 
Output:
Found 853423 10-digit strange numbers with the most significant digit 1.

Found 853423 10-digit strange numbers with the most significant digit 1.
  0.014545 seconds (139 allocations: 13.298 MiB, 29.39% gc time)

Kotlin[edit]

Translation of: Java
import kotlin.math.abs
 
fun digits(n: Int): List<Int> {
var nn = n
val result = mutableListOf<Int>()
while (nn > 0) {
val rem = nn % 10
result.add(0, rem)
nn /= 10
}
return result
}
 
fun isStrange(n: Int): Boolean {
val test = { a: Int, b: Int ->
val abs = abs(a - b)
abs == 2 || abs == 3 || abs == 5 || abs == 7
}
val xs = digits(n)
for (i in 1 until xs.size) {
if (!test(xs[i - 1], xs[i])) {
return false
}
}
return true
}
 
fun main() {
val xs = (100 until 500)
.filter(::isStrange)
.toList()
println("Strange numbers in range [100..500]")
println("(Total: ${xs.size})")
println()
for (i in xs.indices) {
val x = xs[i]
print(x)
if ((i + 1) % 10 == 0) {
println()
} else {
print(' ')
}
}
println()
}
Output:
Strange numbers in range [100..500]
(Total: 87)

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497 

MAD[edit]

            NORMAL MODE IS INTEGER
 
INTERNAL FUNCTION(D)
ENTRY TO PRMDGT.
DD = D
WHENEVER DD.LE.0, DD=-D
FUNCTION RETURN
0 DD.E.2 .OR. DD.E.3 .OR. DD.E.5 .OR. DD.E.7
END OF FUNCTION
 
INTERNAL FUNCTION(A,B)
ENTRY TO REM.
FUNCTION RETURN A-A/B*B
END OF FUNCTION
 
INTERNAL FUNCTION(X)
ENTRY TO STRNGE.
XX = X
LOOP WHENEVER XX.G.9
D0 = REM.(XX,10)
XX = XX/10
D1 = REM.(XX,10)
WHENEVER PRMDGT.(D0-D1), TRANSFER TO LOOP
FUNCTION RETURN 0B
END OF CONDITIONAL
FUNCTION RETURN 1B
END OF FUNCTION
 
PRINT COMMENT $ STRANGE NUMBERS $
THROUGH TEST, FOR I=100, 1, I.GE.500
TEST WHENEVER STRNGE.(I), PRINT FORMAT F, I
 
VECTOR VALUES F = $I4*$
END OF PROGRAM
Output:
STRANGE NUMBERS
 130
 131
 135
 136
 138
 141
 142
 146
 147
 149
 161
 163
 164
 168
 169
 181
 183
 185
 186
 202
 203
 205
 207
 241
 242
 246
 247
 249
 250
 252
 253
 257
 258
 270
 272
 274
 275
 279
 292
 294
 296
 297
 302
 303
 305
 307
 313
 314
 316
 318
 350
 352
 353
 357
 358
 361
 363
 364
 368
 369
 381
 383
 385
 386
 413
 414
 416
 418
 420
 424
 425
 427
 429
 461
 463
 464
 468
 469
 470
 472
 474
 475
 479
 492
 494
 496
 497

Mathematica/Wolfram Language[edit]

 
Select[Range[101, 499],
AllTrue[Partition[IntegerDigits[#], 2, 1], Differences /* First /* PrimeQ] &
]
Output:
{130,131,135,136,138,141,142,146,147,149,161,163,164,168,169,181,183,185,186,202,203,205,207,241,242,246,247,249,250,252,253,257,258,270,272,274,275,279,292,294,296,297,302,303,305,307,313,314,316,318,350,352,353,357,358,361,363,364,368,369,381,383,385,386,413,414,416,418,420,424,425,427,429,461,463,464,468,469,470,472,474,475,479,492,494,496,497}

Nim[edit]

Our program finds the strange numbers with a given number of digits. Filtering is done afterwards. It consumes a lot of memory but is able to find the result in less than a second on our small laptop.

import algorithm, sequtils
 
const PrimeDigits = [2, 3, 5, 7]
 
type
Digit = 0..9
DigitSeq = seq[Digit]
 
func toInt(s: DigitSeq): int =
## Convert a sequence of digits to an int.
for d in s:
result = 10 * result + d
 
 
proc findStrangeNumbers(ndigits: Positive): seq[int] =
## Return the list of strange numbers with "ndigits" digits.
var list: seq[DigitSeq] = toSeq(1..9).mapIt(@[Digit it]) # Starting digits.
for _ in 2..ndigits:
var newList: seq[DigitSeq] # List with one more digit.
for dseq in list:
let last = dseq[^1]
for p in PrimeDigits:
if last - p >= 0:
newList.add dseq & (last - p)
if last + p <= 9:
newList.add dseq & (last + p)
list = move(newList) # "newList" becomes the current list.
result = list.map(toInt)
 
 
var result = sorted(findStrangeNumbers(3).filterIt(it < 500))
echo "Found ", result.len, " strange numbers between 101 and 499."
for i, n in result:
stdout.write n, if (i + 1) mod 15 == 0: '\n' else: ' '
echo()
 
result = findStrangeNumbers(10).filterIt(it div 1_000_000_000 == 1)
echo "\nFound ", result.len, " strange numbers with 10 digits and starting with 1."
Output:
Found 87 strange numbers between 101 and 499.
130 131 135 136 138 141 142 146 147 149 161 163 164 168 169
181 183 185 186 202 203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294 296 297 302 303 305
307 313 314 316 318 350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424 425 427 429 461 463
464 468 469 470 472 474 475 479 492 494 496 497 

Found 853423 strange numbers with 10 digits and starting with 1.

Pascal[edit]

modified recursive version like Julia/Factor using the digits that can follow.
Not dynamically memorizing of all numbers saves much time 200ms -> 4ms.
Count is about 4.6 to the power of Digitscount -> first digit 1 followed by 9 digit -> 4.6^9 = 922190

program strangenumbers;
 
const
dgtMaxCnt = 10;
deltaDgtCnt: array[0..9] of Int32 =(4,4,5,5,5,5,5,5,4,4); // (4*4+6*5)/10 => 4.6
// digits that can follow
DPrmNxtDgt : array[0..9,0..4] of Int32 =((2,3,5,7,0), //0 +2,+3,+5,+7
(3,4,6,8,0), //1 +2,+3,+5,+7
(0,4,5,7,9), //2 -2,+2,+3,+5,+7
(0,1,5,6,8), //3 -3,-2,+2,+3,+5
(1,2,6,7,9), //4 -3,-2,+2,+3,+5
(0,2,3,7,8), //5 -5,-3,-2,+2,+3
(1,3,4,8,9), //6 -5,-3,-2,+2,+3
(0,2,4,5,9), //7 -7,-5,-3,-2,+2
(1,3,5,6,0), //8 -7,-5,-3,-2
(2,4,6,7,0)); //9 -7,-5,-3,-2
type
tDigits = array[0..dgtMaxCnt-1] of Int32;
 
//globals are set to 0
var
Digits : tDigits;
i,Cnt,dgtCnt : Int32;
 
procedure OutPut(const Digits:tDigits);
var
i : Int32;
Begin
For i := 0 to dgtcnt-1 do
write(Digits[i]);
write(' ');
end;
 
procedure NextDigit(var Digits:TDigits;DgtIdx:Int32);
var
idx,dgt :Int32;
Begin
dgt := Digits[DgtIdx];
inc(DgtIdx);
IF DgtIdx < dgtCnt-1 then
Begin
For idx := 0 to deltaDgtCnt[dgt]-1 do
Begin
Digits[DgtIdx]:= DPrmNxtDgt[dgt,idx];
NextDigit(Digits,DgtIdx);
end;
end
else
Begin
For idx := 0 to deltaDgtCnt[dgt]-1 do
Begin
Digits[DgtIdx]:= DPrmNxtDgt[dgt,idx];
inc(cnt);
IF dgtCnt<5 then
Begin
OutPut(Digits);
If cnt mod 16 = 0 then
Writeln;
end;
end;
end;
end;
 
Begin
cnt := 0;
dgtCnt := 3;
Writeln('Count of digits : ', dgtCnt,' in 100..499');
For i := 1 to 4 do
Begin
Digits[0] := i;
NextDigit(Digits,0);
end;
Writeln;
Writeln('Count : ',cnt);
Writeln;
 
cnt := 0;
dgtCnt := 10;
Writeln('Count of digits : ', dgtCnt);
For i := 1 to 1 do
Begin
Digits[0] := i;
NextDigit(Digits,0);
end;
Writeln;
Writeln('Count : ',cnt);
end.
Output:
Count of digits : 3 in 100..499
130 131 135 136 138 141 142 146 147 149 161 163 164 168 169 181 
183 185 186 202 203 205 207 241 242 246 247 249 250 252 253 257 
258 270 272 274 275 279 292 294 296 297 302 303 305 307 313 314 
316 318 350 352 353 357 358 361 363 364 368 369 381 383 385 386 
413 414 416 418 420 424 425 427 429 461 463 464 468 469 470 472 
474 475 479 492 494 496 497 
Count : 87

Count of digits : 10

Count : 853423

Perl[edit]

use strict;
use warnings;
use feature 'say';
use Quantum::Superpositions;
 
sub is_strange {
my @digits = split '', $_;
my @deltas = map { abs $digits[$_-1] - $digits[$_] } 1..$#digits;
all(@deltas) == any(2, 3, 5, 7);
}
 
my($low, $high) = (100, 500);
my $cnt = my @strange = grep { is_strange($_) } $low+1 .. $high-1;
say "Between $low and $high there are $cnt strange numbers:\n" .
(sprintf "@{['%5d' x $cnt]}", @strange[0..$cnt-1]) =~ s/(.{80})/$1\n/gr;
Output:
Between 100 and 500 there are 87 strange numbers:
  130  131  135  136  138  141  142  146  147  149  161  163  164  168  169  181
  183  185  186  202  203  205  207  241  242  246  247  249  250  252  253  257
  258  270  272  274  275  279  292  294  296  297  302  303  305  307  313  314
  316  318  350  352  353  357  358  361  363  364  368  369  381  383  385  386
  413  414  416  418  420  424  425  427  429  461  463  464  468  469  470  472
  474  475  479  492  494  496  497

Phix[edit]

constant diff = {-7,-5,-3,-2,2,3,5,7},
         poss = apply(true,sq_add,{tagset(9,0),{diff}}),
         nxts = apply(true,filter,{poss,{"in"},{{0,9}},{"[]"}})
--       nxts is {{2,3,5,7},{3,4,6,8}..., as per the factor and other entries
 
function strange(integer left, sequence digits, part={})
    sequence res = {}
    for i=1 to length(digits) do
        integer di = digits[i]
        if left=1 then
            string fmt = join(repeat("%d",length(part)+1),"")
            res = append(res,sprintf(fmt,deep_copy(part)&di))
        else
            res &= strange(left-1,nxts[di+1],deep_copy(part)&di)
        end if
    end for
    return res
end function
 
sequence res = strange(3,tagset(4)) -- (3 digit numbers beginning 1..4)
printf(1,"%d strange numbers found: %s\n",{length(res),join(shorten(res,"",5),",")})
Output:
87 strange numbers found: 130,131,135,136,138,...,479,492,494,496,497

stretch goal

Dunno when to quit, me. As there does not appear to be much interest in which 1-digits are strange, I've shown three ways to set ones (output of 0, 10, or 4).

constant diff = {-7,-5,-3,-2,2,3,5,7},
         poss = apply(true,sq_add,{tagset(9,0),{diff}}),
         nxts = apply(true,filter,{poss,{"in"},{{0,9}},{"[]"}}),
--       nxts is {{2,3,5,7},{3,4,6,8}..., as per the factor and other entries
--       ones = columnize({columnize({repeat(0,10),tagset(9,0)}),repeat(0,10)}),
--       ones = columnize({columnize({repeat(0,10),tagset(9,0)}),repeat(1,10)}),
         ones = columnize({columnize({repeat(0,10),tagset(9,0)}),apply(tagset(9,0),is_prime)}),
         twos = columnize({columnize({repeat(1,10),tagset(9,0)}),apply(nxts,length)}),
         dict = new_dict(ones&twos)

function count_strange(integer left, sequence digits, atom res=0)
    for i=1 to length(digits) do
        integer di = digits[i]
        if getd_index({left-1,di},dict)!=NULL then
            res += getd({left-1,di},dict)
        else
            atom prev = res
            res = count_strange(left-1,nxts[di+1],res)
            setd({left-1,di},res-prev,dict)
        end if
    end for
    return res
end function

atom t0 = time()
atom count = count_strange(10,tagset(1))
printf(1,"There are %,d %d-digit strange numbers beginning with 1\n\n",{count,10})

for n=1 to iff(machine_bits()=32?23:28) do
    printf(1,"Total %d-digit strange numbers: %,d\n",{n,count_strange(n,tagset(9,n>1))})
end for

printf(1,"(%s)\n",elapsed(time()-t0))
Output:
There are 853,423 10-digit strange numbers beginning with 1

Total 1-digit strange numbers: 4
Total 2-digit strange numbers: 42
Total 3-digit strange numbers: 194
Total 4-digit strange numbers: 901
Total 5-digit strange numbers: 4,178
Total 6-digit strange numbers: 19,395
Total 7-digit strange numbers: 90,011
Total 8-digit strange numbers: 417,837
Total 9-digit strange numbers: 1,939,540
Total 10-digit strange numbers: 9,003,578
Total 11-digit strange numbers: 41,795,409
Total 12-digit strange numbers: 194,020,644
Total 13-digit strange numbers: 900,672,711
Total 14-digit strange numbers: 4,181,070,893
Total 15-digit strange numbers: 19,409,220,279
Total 16-digit strange numbers: 90,100,876,862
Total 17-digit strange numbers: 418,263,512,702
Total 18-digit strange numbers: 1,941,650,412,637
Total 19-digit strange numbers: 9,013,471,997,782
Total 20-digit strange numbers: 41,842,075,002,263
Total 21-digit strange numbers: 194,238,054,320,527
Total 22-digit strange numbers: 901,686,217,399,477
Total 23-digit strange numbers: 4,185,781,417,010,380
Total 24-digit strange numbers: 19,431,112,295,670,526
Total 25-digit strange numbers: 90,202,542,361,448,337
Total 26-digit strange numbers: 418,735,609,894,371,624
Total 27-digit strange numbers: 1,943,842,229,729,877,443
Total 28-digit strange numbers: 9,023,647,681,353,485,161
(0.0s)

Python[edit]

'''Strange Numbers'''
 
 
# isStrange :: Int -> Bool
def isStrange(n):
'''True if all consecutive decimal digit
pairs in n have a prime difference.
'''

def test(a, b):
return abs(a - b) in [2, 3, 5, 7]
 
xs = digits(n)
return all(map(test, xs, xs[1:]))
 
 
# ------------------- TEST AND DISPLAY -------------------
# main :: IO ()
def main():
'''List and count of Strange numbers'''
 
xs = [
n for n in range(100, 1 + 500)
if isStrange(n)
]
print('\nStrange numbers in range [100..500]\n')
print('(Total: ' + str(len(xs)) + ')\n')
print(
'\n'.join(
' '.join(
str(x) for x in row
) for row in chunksOf(10)(xs)
)
)
 
 
# ----------------------- GENERIC ------------------------
 
# chunksOf :: Int -> [a] -> [[a]]
def chunksOf(n):
'''A series of lists of length n, subdividing the
contents of xs. Where the length of xs is not evenly
divible, the final list will be shorter than n.
'''

def go(xs):
return (
xs[i:n + i] for i in range(0, len(xs), n)
) if 0 < n else None
return go
 
 
# digits :: Int -> [Int]
def digits(n):
'''Component digits of a decimal number.'''
return [int(c) for c in str(n)]
 
 
# MAIN ---
if __name__ == '__main__':
main()
Output:
Strange numbers in range [100..500]

(Total: 87)

130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497

Raku[edit]

sub infix:<>(\x,\y) { abs(x - y)(2, 3, 5, 7) }
 
my ($low,$high) = 100, 500;
my @strange.push: $_ if so all .comb.rotor(2 => -1).map: { .[0].[1] } for $low ^..^ $high;
 
say "Between $low and $high there are {[email protected]} strange numbers:\n";
print @strange.batch(20)».fmt("%4d").join: "\n";
Output:
Between 100 and 500 there are 87 strange numbers:

 130  131  135  136  138  141  142  146  147  149  161  163  164  168  169  181  183  185  186  202
 203  205  207  241  242  246  247  249  250  252  253  257  258  270  272  274  275  279  292  294
 296  297  302  303  305  307  313  314  316  318  350  352  353  357  358  361  363  364  368  369
 381  383  385  386  413  414  416  418  420  424  425  427  429  461  463  464  468  469  470  472
 474  475  479  492  494  496  497

REXX[edit]

Some optimization was added to bypass calculating the absolute value of adjacent decimal digit differences,  
as well as parsing of a number to determine the differences.

/*REXX pgm lists strange integers (within a range) whose decimal digs differ by a prime.*/
numeric digits 20 /*allow processing of larger numbers. */
parse arg LO HI bd . /*obtain optional arguments from the CL*/
if LO=='' | LO=="," then LO= 101 /*Not specified? Then use the default.*/
if HI=='' | HI=="," then HI= 499 /* " " " " " " */
if bd=='' | bd=="," then bd= /* " " " " " " */
begDig= bd\=='' /*look for numbers that start with:" BD*/
show= LO>0 /*indicator if the list is to be shown.*/
!.= 0;  !.2= 1;  !.3= 1;  !.5= 1;  !.7= 1 /*build array of digits that are prime.*/
LO = abs(LO) /*use the absolute value for the search*/
do p=1 for 9; _= -p; if !.p then !._= 1 /*extend array for negatives*/
end /*p*/
$= /*the list of strange numbers (so far)*/
#= 0 /* " number " " " " " */
do j=LO to HI; L= length(j) /*find for strange numbers in the range*/
if L==1 then iterate /*Number too short? Then skip it. */
if bd\=='' then if left(j, 1)\==bd then iterate /*Need leading dig? Maybe skip.*/
 
do k=1 for L-1 /*examine the difference in the digits.*/
parse var j =(k) y +1 z +1 /*get two adjacent decimal digits: Y Z */
dif= y - z /*difference between any adjacent digs.*/
if \!.dif then iterate j /*Difference not prime? Then skip it. */
end /*k*/
#= # + 1 /*bump the number of "strange" numbers.*/
if show then $= $ j /*maybe add the number to the $ list.*/
end /*j*/
/*stick a fork in it, we're all done. */
say commas(#) ' strange numbers found between ' commas(LO) " and " ,
commas(HI) ' (inclusive)'
say
if show then say strip($)
exit 0
/*──────────────────────────────────────────────────────────────────────────────────────*/
commas: parse arg _; do jc=length(_)-3 to 1 by -3; _=insert(',', _, jc); end; return _
output   when using the default inputs:
87  strange numbers found between  101  and  499  (inclusive)

130 131 135 136 138 141 142 146 147 149 161 163 164 168 169 181 183 185 186 202 203 205 207 241 242 246 247 249 250 252 253 257 258
270 272 274 275 279 292 294 296 297 302 303 305 307 313 314 316 318 350 352 353 357 358 361 363 364 368 369 381 383 385 386 413 414
416 418 420 424 425 427 429 461 463 464 468 469 470 472 474 475 479 492 494 496 497
output   when using the inputs of:     -1000000000   2000000000   1
853,423  strange numbers found between  1,000,000,000  and  2,000,000,000  (inclusive)

Ring[edit]

 
load "stdlib.ring"
 
row = 0
see "Strange numbers are:" + nl
 
for n = 100 to 500
flag = 1
str = string(n)
for m = 1 to len(str)-1
num1 = number(str[m])
num2 = number(str[m+1])
pr = fabs(num1-num2)
if not isprime(pr)
flag = 0
exit
ok
next
if flag = 1
see str + " "
row = row + 1
if row % 10 = 0
see nl
ok
ok
next
 
Output:
Strange numbers are:
130 131 135 136 138 141 142 146 147 149 
161 163 164 168 169 181 183 185 186 202 
203 205 207 241 242 246 247 249 250 252 
253 257 258 270 272 274 275 279 292 294 
296 297 302 303 305 307 313 314 316 318 
350 352 353 357 358 361 363 364 368 369 
381 383 385 386 413 414 416 418 420 424 
425 427 429 461 463 464 468 469 470 472 
474 475 479 492 494 496 497 

Ruby[edit]

Translation of: Java
def digits(n)
result = []
while n > 0
rem = n % 10
result.unshift(rem)
n = n / 10
end
return result
end
 
def isStrange(n)
def test(a, b)
abs = (a - b).abs
return abs == 2 || abs == 3 || abs == 5 || abs == 7
end
 
xs = digits(n)
for i in 1 .. xs.length - 1
if !test(xs[i - 1], xs[i]) then
return false
end
end
return true
end
 
xs = []
for i in 100 .. 500
if isStrange(i) then
xs << i
end
end
 
print "Strange numbers in range [100 .. 500]\n"
print "(Total: %d)\n\n" % [xs.length]
 
xs.each_slice(10) do |s|
print s, "\n"
end
Output:
Strange numbers in range [100 .. 500]
(Total: 87)

[130, 131, 135, 136, 138, 141, 142, 146, 147, 149]
[161, 163, 164, 168, 169, 181, 183, 185, 186, 202]
[203, 205, 207, 241, 242, 246, 247, 249, 250, 252]
[253, 257, 258, 270, 272, 274, 275, 279, 292, 294]
[296, 297, 302, 303, 305, 307, 313, 314, 316, 318]
[350, 352, 353, 357, 358, 361, 363, 364, 368, 369]
[381, 383, 385, 386, 413, 414, 416, 418, 420, 424]
[425, 427, 429, 461, 463, 464, 468, 469, 470, 472]
[474, 475, 479, 492, 494, 496, 497]

Sidef[edit]

func generate_from_prefix(limit, p, base) {
 
var seq = [p]
 
for d in (base-1 -> primes) {
for k in ([1, -1]) {
var r = p[0]+(k*d)
next if (r < 0)
next if (r >= base)
var t = [r, p...]
if (t.digits2num(base) <= limit) {
seq << __FUNC__(limit, t, base)...
}
}
}
 
return seq
}
 
func strange_numbers(limit, base = 10, digits = @(^base)) {
digits.map {|p| generate_from_prefix(limit, [p], base)... }\
.map {|t| t.digits2num(base) }\
.sort.uniq
}
 
strange_numbers(500).grep { _ > 100 }.slices(10).each{
.join(' ').say
}
Output:
130 131 135 136 138 141 142 146 147 149
161 163 164 168 169 181 183 185 186 202
203 205 207 241 242 246 247 249 250 252
253 257 258 270 272 274 275 279 292 294
296 297 302 303 305 307 313 314 316 318
350 352 353 357 358 361 363 364 368 369
381 383 385 386 413 414 416 418 420 424
425 427 429 461 463 464 468 469 470 472
474 475 479 492 494 496 497

Wren[edit]

Basic task[edit]

var primes = [2, 3, 5, 7]
var count = 0
var d = []
System.print("Strange numbers in the open interval (100, 500) are:\n")
for (i in 101..499) {
d.clear()
var j = i
while (j > 0) {
d.add(j % 10)
j = (j/10).floor
}
if (primes.contains((d[0] - d[1]).abs) && primes.contains((d[1] - d[2]).abs)) {
System.write("%(i) ")
count = count + 1
if (count % 10 == 0) System.print()
}
}
if (count % 10 != 0) System.print()
System.print("\n%(count) strange numbers in all.")
Output:
Strange numbers in the open interval (100, 500) are:

130 131 135 136 138 141 142 146 147 149 
161 163 164 168 169 181 183 185 186 202 
203 205 207 241 242 246 247 249 250 252 
253 257 258 270 272 274 275 279 292 294 
296 297 302 303 305 307 313 314 316 318 
350 352 353 357 358 361 363 364 368 369 
381 383 385 386 413 414 416 418 420 424 
425 427 429 461 463 464 468 469 470 472 
474 475 479 492 494 496 497 

87 strange numbers in all.

Stretch goal[edit]

Translation of: Julia

... though I've generated the 'possibles' table rather than hard-code it. Runtime about 0.085 seconds which is quick for Wren.

var diffs = [-7, -5, -3, -2, 2, 3, 5, 7]
var possibles = List.filled(10, null)
for (i in 0..9) {
possibles[i] = []
for (d in diffs) {
var sum = i + d
if (sum >= 0 && sum < 10) possibles[i].add(sum)
}
}
 
var places = 10
var start = 1
var strangeOnes = [start]
for (i in 2..places) {
var newOnes = []
for (n in strangeOnes) {
for (nextN in possibles[n%10]) newOnes.add(n*10 + nextN)
}
strangeOnes = newOnes
}
 
System.print("Found %(strangeOnes.count) %(places)-digit strange numbers beginning with %(start).")
Output:
Found 853423 10-digit strange numbers beginning with 1