高级的题解（外加注释）

方法一：

#include <iostream>
using namespace std;

int main() {
    int year, month;
    cin >> year >> month;
    
    // 使用数组存储每月天数（非闰年）
    const int days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    
    // 获取基础天数（2月默认为28天）
    int day = (month >= 1 && month <= 12) ? days[month-1] : 31;
    
    // 闰年判断（仅对2月有效）
    if(month == 2 && ((year%4 == 0 && year%100 != 0) || year%400 == 0)) {
        day++;
    }
    
    cout << day;
    return 0;
}

适合老手

#include <iostream>
#include <stdio.h>
using namespace std;
int main(){
    int year, month,day;
    cin >> year >>month;
    switch (month){
        case 1:day = 31; break;
        case 2:day = 28; break;
        case 3:day = 31; break;
        case 4:day = 30; break;
        case 5:day = 31; break;
        case 6:day = 30; break;
        case 7:day = 31; break;
        case 8:day = 31; break;
        case 9:day = 30; break;
        case 10:day = 31; break;
        case 11:day = 30; break;
        default: day = 31;
    }
    day = (year%4==0&&year%100!=0)||year%400==0?day+=1:day+=0;
    cout << day;
    return 0;
}

适合新手刚学习C++的题解