2021年某月有几天（c++）

#include<iostream>
using namespace std;
int main() {
    int n,d;
    cin >> n;
    switch(n) {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            d = 31;
            break;
        case 4:
        case 6:
        case 9:
        case 11:
            d = 30;
            break;
        case 2:
            d = 28;
            break;
        default:
            cout << "月份输入错误！";
            return 0;
    }
    cout << d;
    return 0;
}

#include<stdio.h>
int main()
{
  int month,day=0;
/*定义月和天*/
  printf("请输入月份：");
  scanf("%d",&month);
/*用switch列表，用于判断这是几月，对应几天*/
  switch (month)
{
  case 2 : day+=29;printf("这是%d月，一共%d天",month,day);break;
  case 4:
  case 6:
  case 9:
  case 11 : day+=30;printf("这是%d月，一共%d天",month,day);break;
  case 1:
  case 3:
  case 5:
  case 7:
  case 8:
  case 10:
  case 12 : day+=31;printf("这是%d月，一共%d天",month,day);break;
  default : printf("请输入正确的年份！");break;
  }
  return 0;
}