比較日期大小一個好的辦法 stringstream

比較日期有時候讓人頭疼，需要考慮很多情況，這裏通過stringstream的方法實現一組日期的排序。

#include <iostream>
using namespace std;
#include<algorithm>
#include<sstream>
#include<iomanip>

struct Date{     //創建日期結構體
	int year, month, day;
};

bool cmp(Date s1,Date s2)
{
	string date1, date2;
	stringstream stream1;
	//把日期輸進流裏。
	stream1 << s1.year << setfill('0') << setw(2) << s1.month << setfill('0') << setw(2) << s1.day;
	//流的值賦給date1.
	date1 = stream1.str();

	stringstream stream2;
	stream2 << s2.year << setfill('0') << setw(2) << s2.month << setfill('0') << setw(2) << s2.day;
	date2 = stream2.str();
       //返回小的值
	return (date1<date2);

}

int main()
{
	int n;
	cin >> n;
	Date date[100];    //創建結構體數組
	for (int i = 0; i < n; i++)
	{
		cin >> date[i].year >> date[i].month >> date[i].day;
	}

	sort(date,date+n,cmp);    //調用
	
	cout << endl;
	for (int i = 0; i < n; i++)
		cout << date[i].year << " " << date[i].month << " " << date[i].day << endl;
}