Smarandache-Wellin primes: Difference between revisions

Content added Content deleted
(→‎{{header|Go}}: Changed in line with Wren solution of which it is a translation.)
(→‎{{header|C}}: Changed in line with Wren solution of which it is a translation.)
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=={{header|C}}==
=={{header|C}}==
{{trans|Wren}}
{{trans|Wren}}
{{libheader|GMP}}
===Basic===
<syntaxhighlight lang="c">#include <stdio.h>
<syntaxhighlight lang="c">#include <stdio.h>
#include <stdlib.h>
#include <stdlib.h>
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#include <string.h>
#include <string.h>
#include <stdint.h>
#include <stdint.h>
#include <gmp.h>

bool isPrime(uint64_t n) {
if (n < 2) return false;
if (n%2 == 0) return n == 2;
if (n%3 == 0) return n == 3;
uint64_t d = 5;
while (d*d <= n) {
if (n%d == 0) return false;
d += 2;
if (n%d == 0) return false;
d += 4;
}
return true;
}


bool *sieve(int limit) {
bool *sieve(int limit) {
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return c;
return c;
}
}

const char *ord(int count) {
return (count == 1) ? "st" :
(count == 2) ? "nd" :
(count == 3) ? "rd" : "th";
}


int main() {
int main() {
bool *c = sieve(400);
bool *c = sieve(12000);
char sw[100] = "";
char sw[6000] = "";
char tmp[20];
char tmp[20];
int swp[3];
int count = 0, p = 1, ix = 0, i;
mpz_t n;
int count = 0, p = 1, i;
while (count < 3) {
mpz_init(n);
printf("The known Smarandache-Wellin primes are:\n");
while (count < 8) {
while (c[++p]);
while (c[++p]);
sprintf(tmp, "%d", p);
sprintf(tmp, "%d", p);
strcat(sw, tmp);
strcat(sw, tmp);
int n = atoi(sw);
mpz_set_str(n, sw, 10);
if (isPrime(n)) swp[count++] = n;
if (mpz_probab_prime_p(n, 15) > 0) {
count++;
size_t le = strlen(sw);
char sws[44];
if (le < 5) {
strcpy(sws, sw);
} else {
strncpy(sws, sw, 20);
strcpy(sws + 20, "...");
strncpy(sws + 23, sw + le - 20, 21);
}
printf("%2d%s: index %4d digits %4ld last prime %5d -> %s\n", count, ord(count), ix+1, le, p, sws);
}
ix++;
}
}
printf("The first 3 Smarandache-Wellin primes are:\n");
for (i = 0; i < 3; ++i) printf("%d ", swp[i]);
printf("\n");


printf("\nThe first 20 Derived Smarandache-Wellin primes are:\n");
int freqs[10] = {0};
int freqs[10] = {0};
uint64_t dswp[3];
count = 0;
count = 0;
p = 1;
p = 1;
while (count < 3) {
ix = 0;
while (count < 20) {
while (c[++p]);
while (c[++p]);
sprintf(tmp, "%d", p);
sprintf(tmp, "%d", p);
for (i = 0; i < strlen(tmp); ++i) freqs[tmp[i]-48]++;
for (i = 0; i < strlen(tmp); ++i) freqs[tmp[i]-48]++;
char dsw[20] = "";
char dsw[40] = "";
for (i = 0; i < 10; ++i) {
for (i = 0; i < 10; ++i) {
sprintf(tmp, "%d", freqs[i]);
sprintf(tmp, "%d", freqs[i]);
strcat(dsw, tmp);
strcat(dsw, tmp);
}
}
int ix = -1;
int idx = -1;
for (i = 0; i < strlen(dsw); ++i) {
for (i = 0; i < strlen(dsw); ++i) {
if (dsw[i] != '0') {
if (dsw[i] != '0') {
ix = i;
idx = i;
break;
break;
}
}
}
}
uint64_t dn = atoll(dsw + ix);
mpz_set_str(n, dsw + idx, 10);
if (isPrime(dn)) dswp[count++] = dn;
}
printf("\nThe first 3 Derived Smarandache-Wellin primes are:\n");
for (i = 0; i < 3; ++i) printf("%ld ", dswp[i]);
printf("\n");
free(c);
return 0;
}</syntaxhighlight>

{{out}}
<pre>
The first 3 Smarandache-Wellin primes are:
2 23 2357

The first 3 Derived Smarandache-Wellin primes are:
4194123321127 547233879626521 547233979727521
</pre>

===Stretch===
{{libheader|GMP}}
<syntaxhighlight lang="c">#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <stdint.h>
#include <gmp.h>

bool *sieve(int limit) {
int i, p;
limit++;
// True denotes composite, false denotes prime.
bool *c = calloc(limit, sizeof(bool)); // all false by default
c[0] = true;
c[1] = true;
for (i = 4; i < limit; i += 2) c[i] = true;
p = 3; // Start from 3.
while (true) {
int p2 = p * p;
if (p2 >= limit) break;
for (i = p2; i < limit; i += 2 * p) c[i] = true;
while (true) {
p += 2;
if (!c[p]) break;
}
}
return c;
}

int main() {
bool *c = sieve(12000);
char sw[6000] = "";
char tmp[20];
int count = 0, p = 1, ix = 0;
mpz_t n;
mpz_init(n);
printf("The 4th to the 8th Smarandache-Wellin primes are:\n");
while (count < 8) {
while (c[++p]);
sprintf(tmp, "%d", p);
strcat(sw, tmp);
mpz_set_str(n, sw, 10);
if (mpz_probab_prime_p(n, 15) > 0) {
if (mpz_probab_prime_p(n, 15) > 0) {
count++;
count++;
if (count > 3) {
printf("%2d%s: index %4d prime %s\n", count, ord(count), ix+1, dsw + idx);
printf("%dth: index %4d digits %4ld last prime %5d\n", count, ix+1, strlen(sw), p);
}
}
}
ix++;
ix++;
}
}
free(c);
free(c);
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{{out}}
{{out}}
<pre>
<pre>
The 4th to the 8th Smarandache-Wellin primes are:
The known Smarandache-Wellin primes are:
4th: index 128 digits 355 last prime 719
1st: index 1 digits 1 last prime 2 -> 2
5th: index 174 digits 499 last prime 1033
2nd: index 2 digits 2 last prime 3 -> 23
6th: index 342 digits 1171 last prime 2297
3rd: index 4 digits 4 last prime 7 -> 2357
7th: index 435 digits 1543 last prime 3037
4th: index 128 digits 355 last prime 719 -> 23571113171923293137...73677683691701709719
8th: index 1429 digits 5719 last prime 11927
5th: index 174 digits 499 last prime 1033 -> 23571113171923293137...10131019102110311033
6th: index 342 digits 1171 last prime 2297 -> 23571113171923293137...22732281228722932297
7th: index 435 digits 1543 last prime 3037 -> 23571113171923293137...30013011301930233037
8th: index 1429 digits 5719 last prime 11927 -> 23571113171923293137...11903119091192311927

The first 20 Derived Smarandache-Wellin primes are:
1st: index 32 prime 4194123321127
2nd: index 72 prime 547233879626521
3rd: index 73 prime 547233979727521
4th: index 134 prime 13672766322929571043
5th: index 225 prime 3916856106393739943689
6th: index 303 prime 462696313560586013558131
7th: index 309 prime 532727113760586013758133
8th: index 363 prime 6430314317473636515467149
9th: index 462 prime 8734722823685889120488197
10th: index 490 prime 9035923128899919621189209
11th: index 495 prime 9036023329699969621389211
12th: index 522 prime 9337023533410210710923191219
13th: index 538 prime 94374237357103109113243102223
14th: index 624 prime 117416265406198131121272110263
15th: index 721 prime 141459282456260193137317129313
16th: index 738 prime 144466284461264224139325131317
17th: index 790 prime 156483290479273277162351153339
18th: index 852 prime 164518312512286294233375158359
19th: index 1087 prime 208614364610327343341589284471
20th: index 1188 prime 229667386663354357356628334581
</pre>
</pre>


Retrieved from "https://rosettacode.org/wiki/Smarandache-Wellin_primes"