【C语言程序设计第四版】例12-1代码

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int prime(int n);

int main(void){
    int n = 2, count = 0;
    FILE * fp;
    
    if ((fp = fopen("prime.txt", "w"))==NULL) {
        printf("File open error!\n");
        exit(0);
    }
    while (count < 500) {
        if (prime(n) != 0) {
            count++;
            fprintf(fp, "%d ", n);
        }
        n++;
    }
    if (fclose(fp)) {
        printf("Can not close the file!\n");
        exit(0);
    }
    return 0;
}

int prime(int m){
    int i, limit;
    
    if (m < 1) {
        return 0;
    }else if(m ==2){
        return 1;
    }else{
        limit=sqrt(m) + 1;
        for (i = 2; i < limit +1; i++) {
            if (m % i == 0) {
                return 0;
            }
        }
        return 1;
    }
}