题解 | 挑7

#include <stdio.h>

int main() {
    int n;
    int a = 0;
    while (scanf("%d", &n) != EOF) { 
          int i;
          int b,c,d,e,f;
          for(i=1;i<=n;i++)
          {
            f = i / 10000;
            e = (i % 10000) / 1000;
            d = (i % 1000) / 100;
            c = (i % 100) / 10;
            b = i % 10;
            if(f == 7 || e == 7 || d== 7 || c== 7 || b == 7) a++;
            if(i % 7 == 0 && f != 7 && e != 7 && d != 7 && c != 7 && b != 7) a++;
          }
          printf("%d",a);
    }
    return 0;
}