笔记

#include <cstdio>

int main()
{
    char str[101];
    fgets(str, 101, stdin);
    int cnt = 0;
    for (int i = 0; str[i] && str[i] != '\n'; i ++)
    {
        if (str[i] >= 48 && str[i] <= 57) cnt ++;
        // 48 == '0' 58 == '9'
    }
    printf("%d\n", cnt);
    return 0;
}