题解 | #日期差值#

#include <bits/stdc++.h>

using namespace std;

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

int is_leap(int year){
	if (year%4==0 && year%100!=0 || year%400 == 0) return 1;
	return 0;
} 

int get_days(int year, int month){
	int res = months[month];
	
	if (month == 2){
		res += is_leap(year); 
	}
	
	return res;
}

int get_days_year(int year){
	if (is_leap(year)) return 366;
	return 365;
}
int main(){
	string datee1, datee2;
	string year1, year2, month1, month2, day1, day2;
	int d1;
	int d2;
	int m1;
	int m2;
	int y1;
	int y2;
	while (cin >> datee1 >> datee2){
		if (datee1 > datee2){
			swap(datee1, datee2);
		}
		year1 = datee1.substr(0,4);
		year2 = datee2.substr(0,4);
		month1 = datee1.substr(4,2);
		month2 = datee2.substr(4,2);
		day1 = datee1.substr(6,2);
		day2 = datee2.substr(6,2);
		
		y1 = stoi(year1);
		y2 = stoi(year2);
		m1 = stoi(month1);
		m2 = stoi(month2);
		d1 = stoi(day1);
		d2 = stoi(day2);
		
		int res = 0;
		for (int i=1; i<=m2-1; i++){
			res += get_days(y2,i);
		}
		res += d2;
		
		for (int i=y1; i<=y2-1; i++){
			res += get_days_year(i);
		}
		
		for (int i=1; i<=m1-1; i++){
			res = res - get_days(y1, i);
		}
		res = res - d1;
		printf("%d\n", res+1);
		
	}
	
	
	return 0;
}