这个代码有逻辑错误，求修改

Question

题目：某年某月某日是当年的第几天(switch月份倒序)

#include<stdio.h>
int judgeyear(int year){
    int flag=0;//平年返回0
    if ((year%4==0 && year%100 !=0) || year%400==0)
           flag=1;//闰年返回1
    return flag;
}
/*本题不考虑日期的合法性，输入的日期是合法的*/
int main(){
    int year,month,day,flag;
    int dayNumber=0;
    scanf("%d%d%d",&year,&month,&day);
    switch (month){
       case 12:dayNumber +=30;
       case 11:dayNumber +=31;
       case 10:dayNumber +=30;
       case 9 :dayNumber +=31;
       case 8 :dayNumber +=31;
       case 7 :dayNumber +=30;
       case 6 :dayNumber +=31;
       case 5 :dayNumber +=30;
       case 4 :dayNumber +=31;
       case 3 :if(flag==0)dayNumber +=28;
                   else dayNumber +=29;//3月的情况,请填写多行代码
       case 2 :dayNumber +=31;//2月的情况,请填写一行代码
       case 1 :dayNumber +=day;break;//1月的情况,请填写多行代码
       default:printf("Input error!");
    }
    printf("%d",dayNumber);
}

Answer 1

第23行修改，供参考：

#include<stdio.h>
int judgeyear(int year){
    int flag=0;//平年返回0
    if ((year%4==0 && year%100 !=0) || year%400==0)
           flag=1;//闰年返回1
    return flag;
}
/*本题不考虑日期的合法性，输入的日期是合法的*/
int main(){
    int year,month,day;    //,flag; 修改
    int dayNumber=0;
    scanf("%d%d%d",&year,&month,&day);
    switch (month){
       case 12:dayNumber +=30;
       case 11:dayNumber +=31;
       case 10:dayNumber +=30;
       case 9 :dayNumber +=31;
       case 8 :dayNumber +=31;
       case 7 :dayNumber +=30;
       case 6 :dayNumber +=31;
       case 5 :dayNumber +=30;
       case 4 :dayNumber +=31;
       case 3 :if(judgeyear(year)==0)//if(flag==0)修改
                   dayNumber +=28;
               else
                   dayNumber +=29;//3月的情况,请填写多行代码
       case 2 :dayNumber +=31;//2月的情况,请填写一行代码
       case 1 :dayNumber +=day;break;//1月的情况,请填写多行代码
       default:printf("Input error!");
    }
    printf("%d",dayNumber);
    return 0;
}