使用引用

#include <iostream>
using namespace std;
struct Time{
	int h;
	int m;
	int s;
};
void timeCompute(Time &t, int sec){	//引用作为形参 
	t.m = t.m + (t.s + sec)/60;	//分钟的进位 
	t.s = (t.s + sec)%60;   //秒数位计算后剩余的时间
	t.h = t.h + t.m/60;	//小时的进位
	t.m = t.m%60;   //分钟位计算后剩余的时间
	t.h = t.h%24;   //小时位取余实现24小时制
} 
int main(){
	int repeat,sec;	//重复次数 
	cin >> repeat;
	struct Time t;  //创建一个time类型的结构体 t
	for(int i = 0; i < repeat; i++){
		scanf("%d:%d:%d", &t.h, &t.m, &t.s); //存入结构体 h m s 
		cin >> sec;	//要度过的秒数 
		timeCompute(t,sec);
		cout << t.h << ":" << t.m << ":" << t.s << endl; 
	}
	return 0;
}

复杂且笨的写法

/*
 * @Author: DEFT:errornotfound@qq.com  V:NOTFOUND6O6 
 * @Date: 2023-02-23 19:44:59
 * @LastEditors: Please set LastEditors
 * @LastEditTime: 2023-03-03 15:19:55
 * @FilePath: \WenkaiC\time_conversion.cpp
 * @Description: 
 * 
 * Copyright (c) 2023 by 1zPeasy, All Rights Reserved. 
 */
#include <iostream>
#include <string>
using namespace std;

int main(int argc, char const *argv[])
{
    int repeat,hour,minute,second,spend_second,add_minute;
    cin >> repeat;        //输入重复次数
    
    for (int i = 0; i < repeat; i++)
    {
        int num_scanned = scanf("%d:%d:%d", &hour, &minute, &second);   //输入时间
        cin >> spend_second;    //输入要度过的秒数
        second = second + spend_second;
        add_minute = second/60; //计算秒数加完到底是要进位多少分钟
        second = second%60; //计算进位分钟后还剩多少秒
        minute = minute + add_minute;   //进位后的分钟
        //判断minute是否需要进位
        if (minute >=60)    //如果更新后的分钟大于等于60
        {
            hour = hour + minute/60;    //计算更新后的hour
            minute = minute % 60;   //分钟数进位后minute还剩多少分钟
        }
        //判断hour是否需要进位
        if (hour  >= 24)    //如果进位后小时数大于=24
        {
            hour = hour %  24;  //更新后的小时数
        }
        cout << "time: " << hour << ":" << minute << ":" << second << endl;
        //判断scanf返回值用来处理错误
        if (num_scanned != 3) {
        
        }
    }
    

    return 0;
}