CalmoSoft primes: Difference between revisions

=={{header|C}}==

<syntaxhighlight lang="c">#include <stdio.h>

#include <stdbool.h>

#include <string.h>

bool isPrime(int n) {

if (n < 2) return false;

if (n%2 == 0) return n == 2;

if (n%3 == 0) return n == 3;

int d = 5;

while (d*d <= n) {

if (n%d == 0) return false;

d += 2;

if (n%d == 0) return false;

d += 4;

}

return true;

}

int main() {

int primes[30] = {2}, sIndices[5], eIndices[5], sums[5];

int i, j, k, temp, sum, si, ei, pc = 1, longest = 0, count = 0;

for (i = 3; i < 100; i += 2) {

if (isPrime(i)) primes[pc++] = i;

}

for (i = 0; i < pc; ++i) {

for (j = pc-1; j >= i; --j) {

temp = j - i + 1;

if (temp < longest) break;

sum = 0;

for (k = i; k <= j; ++k) sum += primes[k];

if (isPrime(sum)) {

if (temp > longest) {

longest = temp;

count = 0;

}

sIndices[count] = i;

eIndices[count] = j;

sums[count] = sum;

++count;

break;

}

}

}

printf("The longest sequence(s) of CalmoSoft primes having a length of %d is/are:\n\n", longest);

for (i = 0; i < count; ++i) {

si = sIndices[i];

ei = eIndices[i];

sum = sums[i];

for (j = si; j <= ei; ++j) printf("%d + ", primes[j]);

printf("\b\b= %d which is prime\n", sum);

if (i < count - 1) printf("\n");

}

return 0;

}</syntaxhighlight>

{{out}}

<pre>

The longest sequence(s) of CalmoSoft primes having a length of 21 is/are:

7 + 11 + 13 + 17 + 19 + 23 + 29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61 + 67 + 71 + 73 + 79 + 83 + 89 = 953 which is prime

</pre>