我的函數有什麼問題，某些數字集可以工作，而其他的則不行？

Question

我應該接受用戶的輸入並說出它是否是有效的日期，但是有些日期打印出有效或無效，然後其他時間只需要輸入並且程序以無輸出結束。

當用戶輸入15/11/11時，它重新排列到11/15/15。如果用戶輸入 12/12/12，它可以正常工作，但04/16/16只是不提供任何輸出。

我的函數中的問題在哪裏引起這個問題？

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

//Declares function 
int check_date(int month, int day, int year); 

int main(void) { 
    int day, month, year; 

    //Asks user for input. 
    printf("Enter a date in this format : MM/DD/YY:"); 


    //If user enters a wrong format it will be invalid. 
    if (scanf_s("%d/%d/%d", &month, &day, &year) == 3) { 
     check_date(day, month, year); 
    } 
    else { 
     printf("You entered a invalid date.\n"); 
    } 
    system("pause"); 
    return 0; 

} 

int check_date(int month, int day, int year) { 

    // If user inputs a valid date this will run. 
    if (month > 0 && month <= 12 && day > 0 && day <= 31 && year > 0 && year <= 99) 
    { 
     switch (month) { 

     //If users month input is 2(febuary) this case will run. 
     case 2: 
      //If it is a leap year and the day 29 is entered it is invalid. 
      if (year % 4 == 0) { 
       if (day == 29) { 
        printf("Invalid date."); 
       } 
       else { 
        printf("You entered a valid date, %d/%d/%d", month, day, year); 
       } 
       break; 
     //If user inputs 4 this case will run. 
     case 4: 
      //There is not 31 days in this month. 
      if (day == 31) { 
       printf("Invalid date."); 
      } 
      else { 
       printf("You entered a valid date, %d/%d/%d", month, day, year); 
      } 
      break; 

     //If user inputs 4 this case will run. 
     case 6: 
      //There is not 31 days in this month. 
      if (day == 31) { 
       printf("Invalid date."); 
      } 
      else { 
       printf("You entered a valid date, %d/%d/%d", month, day, year); 
      } 
      break; 

     //If user inputs 4 this case will run. 
     case 9: 
      //There is not 31 days in this month. 
      if (day == 31) { 
       printf("Invalid date."); 
      } 
      else { 
       printf("You entered a valid date, %d/%d/%d", month, day, year); 
      } 
      break; 
     //If user inputs 4 this case will run. 
     case 11: 
      //There is not 31 days in this month. 
      if (day == 31) { 
       printf("Invalid date."); 
      } 
      else { 
       printf("You entered a valid date, %d/%d/%d", month, day, year); 
      } 
      break; 
     //If user enters any other date other then the cases it is valid. 
     default: 
      printf("You entered a valid date, %d/%d/%d", month, day, year); 
      break; 
     } 
      //If user enters anything other then the correct format, this else will run. 
      else { 
       printf("You entered a invalid date."); 
      } 
     } 
    } 
} 

Answer 1

試試這個代碼，更簡單

/*C program to validate date (Check date is valid or not).*/ 

#include <stdio.h> 

int main() 
{ 
    int dd,mm,yy; 

    printf("Enter date (DD/MM/YYYY format): "); 
    scanf("%d/%d/%d",&dd,&mm,&yy); 

    //check year 
    if(yy>=1900 && yy<=9999) 
    { 
     //check month 
     if(mm>=1 && mm<=12) 
     { 
      //check days 
      if((dd>=1 && dd<=31) && (mm==1 || mm==3 || mm==5 || mm==7 || mm==8 || mm==10 || mm==12)) 
       printf("Date is valid.\n"); 
      else if((dd>=1 && dd<=30) && (mm==4 || mm==6 || mm==9 || mm==11)) 
       printf("Date is valid.\n"); 
      else if((dd>=1 && dd<=28) && (mm==2)) 
       printf("Date is valid.\n"); 
      else if(dd==29 && mm==2 && (yy%400==0 ||(yy%4==0 && yy%100!=0))) 
       printf("Date is valid.\n"); 
      else 
       printf("Day is invalid.\n"); 
     } 
     else 
     { 
      printf("Month is not valid.\n"); 
     } 
    } 
    else 
    { 
     printf("Year is not valid.\n"); 
    } 

    return 0;  
}