C语言实现日期转换问题（要求考虑闰年的问题）

按如下函数原型用函数编程解决如下的日期转换问题（要求考虑闰年的问题）：
/* 函数功能：  对给定的某年某月某日，计算它是这一年的第几天
函数参数：  整型变量year、month、day，分别代表年、月、日          
函数返回值：这一年的第几天 */
int  DayofYear(int year, int month, int day);
/* 函数功能：    对给定的某一年的第几天，计算它是这一年的第几月第几日
函数入口参数：整型变量year，存储年
                 整型变量yearDay，存储这一年的第几天
函数出口参数：整型指针pMonth，指向存储这一年第几月的整型变量
                 整型指针pDay，指向存储第几日的整型变量
函数返回值：  无 */
void  MonthDay(int year, int yearDay, int *pMonth, int *pDay);
输出如下菜单，用switch语句实现根据用户输入的选择执行相应的操作。
1. year/month/day -> yearDay
2. yearDay -> year/month/day
3. Exit
Please enter your choice:
输入提示信息：
"Please enter year, month, day:"
"Please enter year, yearDay:"
输入格式：
"%d,%d,%d"
"%d,%d"
输出提示信息和格式：
"yearDay = %d\n"
"month = %d, day = %d\n"

#include    <stdio.h>
#include    <stdlib.h>
int  DayofYear(int year, int month, int day);
void  MonthDay(int year, int yearDay, int *pMonth, int *pDay);
void  Menu(void);
int dayTab[2][13] = {{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},                           {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}};
int main()
{                                
    int    year, month, day, yearDay;
    char   c;
    Menu();             /* 调用Menu函数显示一个固定式菜单 */
    c = getchar();      /* 输入选择 */
    switch (c)          /* 判断选择的是何种操作 */
    {                                
    case '1':
        printf("Please enter year, month, day:");
        scanf("%d,%d,%d", &year, &month, &day);
        yearDay = DayofYear(year, month, day);
        printf("yearDay = %d\n", yearDay);
        break;
    case '2':
        printf("Please enter year, yearDay:");
        scanf("%d,%d", &year, &yearDay);
        MonthDay(year, yearDay, &month, &day);
        printf("month = %d,day = %d\n", month, day);
        break;
    case '3':
        exit(0);   /* 退出程序的运行 */
    default:
        printf("Input error!");
    }
    return 0;
}                                
/* 函数功能：对给定的某年某月某日，计算并返回它是这一年的第几天 */
int  DayofYear(int year, int month, int day)
{                                
    int  i, leap;
    /* 若year为闰年，即leap值为1，则用第1行元素dayTab[1][i]计算；
    否则leap值为0，用第0行dayTab[0][i]计算 */
    leap = ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);
    for (i = 1; i < month; i++)
    {                                
        day = day + dayTab[leap][i];
    }
    return day;         /* 返回计算出的day的值 */
}                                
/* 函数功能：对给定的某一年的第几天，计算它是这一年的第几月第几日 */
void  MonthDay(int year, int yearDay, int *pMonth, int *pDay)
{                                
    int  i, leap;
    leap = ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);
    for (i = 1; yearDay > dayTab[leap][i]; i++)
    {                                
        yearDay = yearDay - dayTab[leap][i];
    }
    *pMonth = i;        /* 将计算出的月份值赋值给pMonth所指向的变量 */
    *pDay = yearDay;   /* 将计算出的日号赋值给pDay所指向的变量 */
}                                
/* 函数功能：显示菜单 */
void  Menu(void)
{                                
    printf("1. year/month/day -> yearDay\n");
    printf("2. yearDay -> year/month/day\n");
    printf("3. Exit\n");
    printf("Please enter your choice:");
}                               

leap = ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);

#include<stdio.h>
int  DayofYear(int year, int month, int day);
void  MonthDay(int year, int yearDay, int *pMonth, int *pDay);
main()
{
    int n,year, yearDay, month, day,Month, Day;
    do
    {
        printf("1. year/month/day -> yearDay\n");
        printf("2. yearDay -> year/month/day\n");
        printf("3. Exit\n");
        printf("Please enter your choice:");
        scanf("%d", &n);
        switch (n)
        {
        case 1:
        {
            yearDay = DayofYear(year, month, day);
            printf("yearDay = %d\n", yearDay);
            break;
        }
        case 2:
        {
            MonthDay(year, yearDay, &Month, &Day);
            break;
        }
        }
    }while(n!=3);
}
int  DayofYear(int year, int month, int day)
{
    int yearDay = 0, i;
    int days[12];
    printf("Please enter year, month, day:");
    scanf("%d,%d,%d", &year, &month, &day);
    if ((year % 4 == 0&&year%100!=0)||(year%100==0&&year%400==0))
    {
        days[0]=31;
        days[1]=29;
        days[2]=31;
        days[3]=30;
        days[4]=31;
        days[5]=30;
        days[6]=31;
        days[7]=31;
        days[8]=30;
        days[9]=31;
        days[10]=30;
        days[11]=31;
    }
    else
    {
        days[0]=31;
        days[1]=28;
        days[2]=31;
        days[3]=30;
        days[4]=31;
        days[5]=30;
        days[6]=31;
        days[7]=31;
        days[8]=30;
        days[9]=31;
        days[10]=30;
        days[11]=31;
    }
    for (i = 0; i < month - 1; i++)
    {
        yearDay += days[i];
    }
    yearDay += day;
    return yearDay;
}
void  MonthDay(int year, int yearDay, int *pMonth, int *pDay)
{
    int month = 0, day;
    int days[12];
    printf("Please enter year, yearDay:");
    scanf("%d,%d", &year, &yearDay);
    if ((year % 4 == 0&&year%100!=0)||(year%100==0&&year%400==0))
    {
        days[0]=31;
        days[1]=29;
        days[2]=31;
        days[3]=30;
        days[4]=31;
        days[5]=30;
        days[6]=31;
        days[7]=31;
        days[8]=30;
        days[9]=31;
        days[10]=30;
        days[11]=31;
    }
    else
    {
        days[0]=31;
        days[1]=28;
        days[2]=31;
        days[3]=30;
        days[4]=31;
        days[5]=30;
        days[6]=31;
        days[7]=31;
        days[8]=30;
        days[9]=31;
        days[10]=30;
        days[11]=31;
    }
    do
    {
        yearDay -= days[month];
        month++;
    }
    while (yearDay >= days[month]);
    day = yearDay;
    printf("month = %d, day = %d\n", month+1, day);
}