how many days between two date?

a263.c

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

int leap(int input) //閏年判斷
{
    if(input%400==0)
    {
        return 1;
    }
    else if(input%4==0 && input%100!=0)
    {
        return 1;
    }
    else
        return 0;
}

int headMonth(int month, int date, int year) //測資給的當月(開頭年)
{
    int re=0;
    if(month==1 || month==3 || month==5 || month==7 || month==8 || month==10 || month==12)
        re+=31-date;
    else if(month==2 && leap(year))
        re+=29-date;
    else if(month==2 && !leap(year))
        re+=28-date;
    else if(month==4 || month==6 || month==9 || month==11)
        re+=30-date;

    return re;
}

int monthCount1(int month, int year)//開頭年還沒經過的月份
{
    int re=0;
    while(month<12)
    {
        month++;
        if(month==2 && leap(year))
            re+=29;
        else if(month==2 && !leap(year))
            re+=28;
        else if(month==3 || month==5 || month==7 || month==8 || month==10 || month==12)
            re+=31;
        else if(month==4 || month==6 || month==9 || month==11)
            re+=30;
    }

    return re;
}

int monthCount2(int month, int year)//結尾年已經過的月份
{
    int re=0,month1=1;
    while(month1<month)
    {
        if(month1==1 || month1==3 || month1==5 || month1==7 || month1==8 || month1==10 || month1==12)
            re+=31;
        else if(month1==2 && leap(year))
            re+=29;
        else if(month1==2 && !leap(year))
            re+=28;
        else if(month1==4 || month1==6 || month1==9 || month1==11)
            re+=30;
        
        month1++;
    }

    return re;
}

int yearCount(int year1, int year2)//計算跨過的年份
{
    int re=0;
    while(year2+1<year1)
    {
        year2++;
        if(leap(year2))
            re+=366;
        else
            re+=365;

    }
    return re;
}

int main()
{
    int year1,year2,month1,month2,date1,date2;
    while(scanf("%d %d %d",&year1,&month1,&date1)==3)
    {
        scanf("%d %d %d",&year2,&month2,&date2);

        int tmp,total=0; //先處理測資讓第一個測資一定大於第二個
        if((year1<year2) || ((year1==year2) && (month1<month2)) || ((year1==year2) && (month1==month2) && (date1<date2)))
        {
            tmp=year1;
            year1=year2;
            year2=tmp;

            tmp=month1;
            month1=month2;
            month2=tmp;

            tmp=date1;
            date1=date2;
            date2=tmp;
        }

        if(year1-year2>=2)
        {
            total+=date1;
            total+=headMonth(month2,date2,year2)+monthCount1(month2,year2)+monthCount2(month1,year1)+yearCount(year1,year2);
        }
        else if(year1-year2==1) //年份相差1
        {
            total+=date1;
            total+=headMonth(month2,date2,year2)+monthCount1(month2,year2)+monthCount2(month1,year1);
        }
        else //同年
        {
            if(month1!=month2)
            {
                total+=date1;
                total+=headMonth(month2,date2,year2);
                while(month1!=month2+1)
                {
                    month2++;
                    if(month2==1 || month2==3 || month2==5|| month2==7 || month2==8 || month2==10 || month2==12)
                        total+=31;
                    else if(month2==2 && leap(year2))
                        total+=29;
                    else if(month2==2 && !leap(year2))
                        total+=28;
                    else if(month2==4 || month2==6 || month2==9 || month2==11)
                        total+=30;
                }
            }
            else
                total+=date1-date2;
        }

        printf("%d\n",total);
    }
}