View Code of Problem 56

//
//  main.c
//  a
//
//  Created by rex on 16/9/14.
//  Copyright © 2016年 rex. All rights reserved.
//

#include <stdio.h>
#include <string.h>

int main() {
    int h1, m1, s1, h2, m2, s2, sum1, sum2, res;
    scanf("%d:%d:%d%d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
    sum1 = h1 * 60 * 60 + m1 * 60 + s1;
    sum2 = h2 * 60 * 60 + m2 * 60 + s2;
    while(sum2 < sum1) {
        sum2 += 24 * 60 * 60;
    }
    res = sum2 - sum1;
    printf("%d:%02d:%02d", res / 60 / 60, (res % 3600)/60, (res%3600)%60);
    return 0;
}