题解 | 日期累加

#include <iostream>
using namespace std;

void nextDay(int& year, int& month, int& day) {
	// 每个月份的天数数组
	int dayOfMonth[] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };
	// 是否闰年判断条件
	bool isLeap = year % 400 == 0 || year % 4 == 0 && year % 100 != 0;
	if (isLeap) {
		dayOfMonth[2] = 29;  // 闰年2月多一天
	}
	day++;
	if (day > dayOfMonth[month]) {
		day = 1;
		month++;
	}
	if (month > 12) {
		month = 1;
		year++;
	}
}

int main() {
	int year, month, day, n, m;
	cin >> m;
	for (int i = 0; i < m;i++) {
		cin >> year >> month >> day >> n;
		while (n >= 1) {  // 加上若干天不含当前天 带等号 几天之后含当前天 不带等号
			nextDay(year, month, day);
			n--;
		}
		if (month <= 9 && day <= 9) {
			cout << year << "-0" << month << "-0" << day << endl;
		}
		else if (day <= 9) {
			cout << year << "-" << month << "-0" << day << endl;
		}
		else if (month <= 9) {
			cout << year << "-0" << month << "-" << day << endl;
		}
		else {
			cout << year << "-" << month << "-" << day << endl;
		}
	}
	return 0;
}

// c语言格式化输出 %02d  0填充，最小宽度2