Hailstone sequence: Difference between revisions
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The hailstone sequence has length 112
77031 has the longest sequence of 351
</pre>
==={{header|PL/I-80}}===
<lang PL/I>hailstone_demo: proc options (main);
%replace
true by '1'b,
false by '0'b;
dcl
(slen, longest) fixed bin(15),
(n, n_longest,limit) fixed decimal(12),
answer char(1);
put skip list ('Display hailstone sequence for what number? ');
get list (n);
slen = hailstone(n, true);
put skip list ('Sequence length = ', slen);
put skip(2) list ('Search for longest sequence (y/n)? ');
get list (answer);
if ((answer ^= 'y') & (answer ^= 'Y')) then stop;
put list ('Search to what limit? ');
get list (limit);
longest = 1;
n = 2;
do while (n < limit);
slen = hailstone(n, false);
if slen > longest then
do;
longest = slen;
n_longest = n;
end;
n = n + 1;
end;
put skip edit ('Longest sequence =',longest,' for n =',n_longest)
(a,f(4),a,f(6));
/* compute, and optionally display, hailstone sequence for n */
hailstone:
procedure(n, show) returns (fixed binary);
dcl
(len, col) fixed binary,
(n, k) fixed decimal(12),
show bit(1);
/* make local copy since n is passed by reference */
k = n;
col = 1;
len = 1;
do while ((k ^= 1) & (k > 0));
if (show) then /* print 8 columns across */
do;
put edit (k) (f(8));
col = col + 1;
if col > 8 then
do;
put skip;
col = 1;
end;
end;
if (mod(k,2) = 0) then
k = k / 2;
else
k = k * 3 + 1;
len = len + 1;
end;
if (show) then put edit (k) (f(8));
return (len);
end hailstone;
end hailstone_demo;
</lang>
{{out}}
<pre>Display hailstone sequence for what number? 27
27 82 41 124 62 31 94 47
142 71 214 107 322 161 484 242
121 364 182 91 274 137 412 206
103 310 155 466 233 700 350 175
526 263 790 395 1186 593 1780 890
445 1136 668 334 167 502 251 754
377 1132 566 283 850 425 1276 638
319 958 479 1438 719 2158 1079 3238
1619 4858 2429 7288 3644 1822 911 2734
1367 4102 2051 6154 3077 9232 4616 2308
1154 577 1732 866 433 1300 650 325
976 488 244 122 61 184 92 46
23 70 35 106 53 160 80 40
20 10 5 16 8 4 2 1
Sequence length = 112
Search for longest sequence (y/n)? y
Search to what limit? 100000
Longest sequence = 351 for n = 77031
</pre>
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