题解 | #日期累加#

#include <iostream>
#include <cstdio>
#include <array>
using namespace std;

bool isLeapYear(int year) {
    return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
}

array<array<int, 13>, 2> dayTab = {
    {   {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
        {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
    }
};


int main() {
    int n;
    while (cin >> n) { // 注意 while 处理多个 case
        for (int i = 0; i < n; i++) {
            int year, month, day;
            int add;
            cin >> year >> month >> day >> add;
            add += (day-1);
            day = 1; // 从第一天开始，方便计算
            int isLeap = isLeapYear(year);
            while (add > dayTab[isLeap][month]) {
                add -= dayTab[isLeap][month];
                day = 1;
                if (month > 12) {
                    year ++;
                    isLeap = isLeapYear(year); // 跨年更新闰年标记
                    month = 1;
                } else {
                    month++;
                }
            }
            day += add;
            printf("%04d-%02d-%02d\n", year, month, day);
        }
        return 0;
    }
}
// 64 位输出请用 printf("%lld")