求<=n的所有素数
#include <stdio.h>#include <stdlib.h>#include <unistd.h>int main(int argc, char **argv){ if (argc != 2) { printf("Usage: ./a.out <num>\n"); exit(EXIT_FAILURE); } int n = atoi(argv); int arr; // init int i; for (i = 0; i <= n; i++) arr = i; int p; for (p = 2; p < n; p++) for ( i = p + 1; i <= n; i++) if (i % p == 0) arr = 0; // display all prime number for (i = 0; i <= n; i++) if (arr != 0) printf("%d\n", arr); exit(EXIT_SUCCESS);}
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