判断某年某月某日是这一年第几天

判断某年某月某日是这一年的第几天 程序未报错 不知道为什么结果一直不对

#include 
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char** argv) {
    int year,month,day,a,b,c,d;
    a==0;
    b==0;
    c==0;
    d==0;
    a==(month-1)*31+day+29;
    b==(month-1)*30+day+29;
    c==day;
    d==31+day;
    cout<<"Input year,month,day: "<>year>>month>>day;
    if(year%4==0&&year%100!=0||year%100==0)
      switch(month){
      case 1:
      cout<<"Days of year: "<break;
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12:
      cout<<"Days of year: "<break;
      case 4:
      case 6:
      case 9:
      case 11:
      cout<<"Days of year: "<break;
      case 2:
      cout<<"Days of year: "<break;
      }
      else 
          switch(month)
          {
              case 1:
      cout<<"Days of year: "<break;
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12:
      cout<<"Days of year: "<-1;
      break;
      case 4:
      case 6:
      case 9:
      case 11:
      cout<<"Days of year: "<-1;
      break;
      case 2:
      cout<<"Days of year: "<break;
}
      return 0;
}

先输入再计算，赋值用一个=，不是两个

#include <iostream>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
 
int main(int argc, char** argv) {
    int year,month,day,a,b,c,d;
    a=0;
    b=0;
    c=0;
    d=0;
  
    cout<<"Input year,month,day: "<<endl;
    cin>>year>>month>>day;
    a=(month-1)*31+day+29;
    b=(month-1)*30+day+29;
    c=day;
    d=31+day;
    if(year%4==0&&year%100!=0||year%100==0)
      switch(month){
      case 1:
      cout<<"Days of year: "<<c;
      break;
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12:
      cout<<"Days of year: "<<a;
      break;
      case 4:
      case 6:
      case 9:
      case 11:
      cout<<"Days of year: "<<b;
      break;
      case 2:
      cout<<"Days of year: "<<d;
      break;
      }
      else 
          switch(month)
          {
              case 1:
      cout<<"Days of year: "<<c;
      break;
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12:
      cout<<"Days of year: "<<a-1;
      break;
      case 4:
      case 6:
      case 9:
      case 11:
      cout<<"Days of year: "<<b-1;
      break;
      case 2:
      cout<<"Days of year: "<<d;
      break;
}
      return 0;
}
 
 

• 给你找了一篇非常好的博客，你可以看看是否有帮助，链接：输入某年某月某日，判断这一天是这一年的第几天？

这个肯定不对，你都没输入就计算a,b了
要先输入然后再计算，而且好多情况都没有输出

#include <iostream>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
 
int main(int argc, char** argv) {
    int year,month,day,days = 0;
    int second = 29;
    cout<<"Input year,month,day: "<<endl;
    cin>>year>>month>>day;
    if((year%4==0&&year%100!=0)||year%100==0){
        second = 29;
    }
    else{
        second = 28;
    }
    for(int i = 1;i <= month;i++){
            if(i == 1 || i == 3 || i == 5 || i == 7 || i == 8 || i == 10 || i ==12){
                days += 31;
            }else if(i == 2){
                days += second;
            }else{
                days += 30;
            }
    }
    days += day;
    printf("Days of year: %d\n",days);
    return 0;
}