题解 | #日期差值#

#include <cstdio>
#include <iostream>
using namespace std;

int IsLeapYear(int year){
    return (year % 400 == 0 || (year % 100 != 0 && year % 4 == 0));
}

int main() {
    int year1,year2,month1,month2,day1,day2;
    int mon_day[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}};
    while (scanf("%4d%2d%2d",&year1,&month1,&day1)!=EOF) {
        scanf("%4d%2d%2d",&year2,&month2,&day2);
        
        int totalDay = 0;
        //思路是先判断两个年份的大小，大的年份就算日期相对于当年的1月1日的差值，小的年份算相对于当年的12月31日的差值
        //再根据两个年份中间相差几年进行，闰年就加366，平年就加365，例如：2013与2011中间只差2012年的366天，最后根据规定再多加一天。
	  //相同年份时，分别算距离当年12月31日相差多少天，最后相减取绝对值+1就是最终相差的天数
        if (year1>year2) {
            for (int i = month2 ; i <= 12 ; ++i ) {
                totalDay += mon_day[IsLeapYear(year2)][i] - day2;
                day2 = 0;
            }
            for (int j = 0; j < month1 ; ++j ) {
                totalDay += mon_day[IsLeapYear(year1)][j] + day1;
                day1 = 0;
            }
            for (int k = year2; k < year1-1; k++) {
                if (IsLeapYear(k)) {
                    totalDay += 366;
                }else {
                    totalDay += 365;
                }
            }
            totalDay++;
        }else if(year1<year2) {
            for (int i = month1 ; i <= 12 ; ++i ) {
                totalDay += mon_day[IsLeapYear(year1)][i] - day1;
                day1 = 0;
            }
            for (int j = 0; j < month2 ; ++j ) {
                totalDay += mon_day[IsLeapYear(year2)][j] + day2;
                day2 = 0;
            }
            for (int k = year1; k < year2-1; k++) {
                if (IsLeapYear(k)) {
                    totalDay += 366;
                }else {
                    totalDay += 365;
                }
            }
            totalDay++;
        }else {
            int tDay1 = 0,tDay2 = 0;
            for (int i = month1 ; i <= 12 ; ++i ) {
                tDay1 += mon_day[IsLeapYear(year1)][i] - day1;
                day1 = 0;
            }
            for (int i = month2 ; i <= 12 ; ++i ) {
                tDay2 += mon_day[IsLeapYear(year2)][i] - day2;
                day2 = 0;
            }
            tDay1-tDay2 > 0 ? totalDay = tDay1-tDay2+1 : totalDay = tDay2-tDay1+1;
        }
        printf("%d",totalDay);
    }
    return 0;
}