题解 | #添加逗号#

#include <stdio.h>

int main() {
    
    unsigned int num = 0;
    int arr[11] = {0};
    scanf("%u",&num);
    int flag = 0;
    while (num > 0)
    {
        int cnt = num % 10;
        arr[flag] = cnt;
        num /= 10;
        flag++;
    }

    for (int i = flag-1; i >= 0; i--)
    {
        if (i % 3 ==0 && i != 0)
        {
            printf("%d,",arr[i]);
        }
        else 
        {
            printf("%d",arr[i]);
        }
    }
    return 0;
}