题解 | 打印日期

#include <iostream>

using std::cout;
using std::cin;
using std::endl;

int main() {
    int y, n;
    while (cin >> y >> n) {
        bool flag = false;
        if ((y % 4 == 0) && (y % 100 != 0) || (y % 400 == 0))
            flag = true;

        int m = 1;
        switch (1) {
            case 1:
                if (n <= 31) break;
				n -= 31;
				m++;
            case 2:
                if (flag) {
                    if( n <= 29) break;
				  	n-= 29;
				  	m++;
                } else {
                    if(n <= 28) break;
				  	n -= 28;
				  	m++;
                }
            case 3:
                if (n <= 31) break;
				n -= 31;
				m++;
            case 4:
                if (n <= 30) break;
                n -= 30;
                m++;
            case 5:
                if (n <= 31) break;
                n -= 31;
                m++;
            case 6:
                if (n <= 30) break;
                n -= 30;
                m++;
            case 7:
                if (n <= 31) break;
                n -= 31;
                m++;
            case 8:
                if (n <= 31) break;
                n -= 31;
                m++;
            case 9:
                if (n <= 30) break;
                n -= 30;
                m++;
            case 10:
                if (n <= 31) break;
                n -= 31;
                m++;
            case 11:
                if (n <= 30) break;
                n -= 30;
                m++;
        }
        // 按照yyyy-mm-dd格式输出日期
        cout << y << '-';
        if (m < 10) cout << 0;
        cout << m << '-';
        if (n < 10) cout << 0;
        cout << n << endl;
    }

    return 0;
}