Descending primes: Difference between revisions

=={{header|C}}==

{{trans|C#}}

<lang C>#include <stdio.h>

int ispr(unsigned int n) {

if ((n & 1) == 0 || n < 2) return n == 2;

for (unsigned int j = 3; j * j <= n; j += 2)

if (n % j == 0) return 0; return 1; }

int main() {

unsigned int c = 0, nc, pc = 9, i, a, b, l,

ps[128], nxt[128];

for (a = 0, b = 1; a < pc; a = b++) ps[a] = b;

while (1) {

nc = 0;

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

if (ispr(a = ps[i]))

printf("%8d%s", a, ++c % 5 == 0 ? "\n" : " ");

for (b = a * 10, l = a % 10 + b++; b < l; b++)

nxt[nc++] = b;

}

if (nc > 1) for(i = 0, pc = nc; i < pc; i++) ps[i] = nxt[i];

else break;

}

printf("\n%d descending primes found", c);

}</lang>

{{out}}

Same as C#