#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a, n;
    cin >> a >> n;
    if (a % 400 == 0)
    {
        if (n == 2)
        {
            cout << "29";
        }
        else if (n == 1 || n == 3 || n == 5 || n == 7 || n == 8 || n == 10 || n == 12)
        {
            cout << "31";
        }
        else
        {
            cout << "30";
        }
    }
    else if (a % 4 == 0 && a % 100 != 0)
    {
        if (n == 2)
        {
            cout << "29";
        }
    }
    else if (n == 2)
    {
        cout << "28";
    }
    if (n == 1 || n == 3 || n == 5 || n == 7 || n == 8 || n == 10 || n == 12)
    {
        cout << "31";
    }
    else if (n == 4 || n == 6 || n == 9 || n == 11)
    {
        cout << "30";
    }
    return 0;
}

跟P1092一摸一样

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int x,y;
    cin>>x>>y;
    if (y==2)
        if (x%4==0&&(x%400==0||x%100!=0))
            cout<<29;
        else
            cout<<28;
    else
        if (y==1||y==3||y==5||y==7||y==8||y==10||y==12)
            cout<<31;
        else
            cout<<30;
    return 0;
}