【题目】

计算给定两个日期之间相差天数？

【解析】

//May 05 2015 By 12052010 测试通过，望采纳
#include<stdio.h>

//判断闰年，如果是闰年返回1，否则返回0
int isYear(int year){
    return (year%4==0)&&( year %400==0 || year %100!= 0) ? 1:0;
}

//返回该年 year 该月 month 的最大天数
int getDayOfMonth(int year , int month) {

    int dayArr[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};

    return (month == 2 && isYear(year)==1) ? dayArr[month]+1 : dayArr[month] ;
}

//获取两个日期之间的天数，第一个日期必须比第二个日期小  ：)
int getTotalDay(int year1,int month1,int day1,int year2,int month2,int day2){

    long total = 0;

    for(int year = year1; year < year2 ;  year ++ ){
        total = total + 365;
        if(isYear(year)==1)
            total ++;
    }

    for(int month =1; month < month2; month ++ ){
        total = total + getDayOfMonth(year2,month);
    }

    total = total + day2;

    for(int month=1 ; month < month1; month ++ ){
         total = total - getDayOfMonth(year1,month);
    }

    return total - day1;

}

int main(){

    int year1 ,month1,day1;
    int year2, month2,day2;

    do{//控制日期输进合法，同时year1应该小于year2
            printf("\nInput year1-month1-day1\n(such as 2012-12-12) : ");
            scanf("%d-%d-%d", &year1,&month1,&day1);
    } while( year1 <0 || month1<1 || month1>12 || day1<1|| day1> getDayOfMonth(year1,month1));


    do{//控制日期输进合法
            printf("\n\n\nInput year2-month2-day2\n(such as 2014-12-12) : ");
            scanf("%d-%d-%d", &year2,&month2,&day2);
    } while( year2 <0 || year2 <year1|| month2<1 || month2>12 || day2<1|| day2> getDayOfMonth(year2,month2));



    printf("\nBetween two date have: %ld  days \n\n\n", getTotalDay(year1,month1,day1,year2,month2,day2));
    return 0;
}

参考：https://zhidao.baidu.com/question/1542125532759953627.html