# 如何在C/C++中对日期数组进行排序？

``````Input:
Date arr[] = {{20, 1, 2014}, {25, 3, 2010}, { 3, 12, 1676}, {18, 11, 1982}, {19, 4, 2015}, { 9, 7, 2015}}

Output:
Date arr[] = {{ 3, 12, 1676}, {18, 11, 1982}, {25, 3, 2010}, {20, 1, 2014}, {19, 4, 2015}, { 9, 7, 2015}}``````

C++中的排序功能

。我们可以编写自己的比较函数, 该函数首先比较年份, 然后比较几个月, 然后比较几天。

``````//C++ program to sort an array of dates
#include<bits/stdc++.h>
using namespace std;

//Structure for date
struct Date
{
int day, month, year;
};

//This is the compare function used by the in-built sort
//function to sort the array of dates.
//It takes two Dates as parameters (const is
//given to tell the compiler that the value won't be
//changed during the compare - this is for optimization..)

//Returns true if dates have to be swapped and returns
//false if not. Since we want ascending order, we return
//true if the first Date is less than the second date
bool compare( const Date &d1, const Date &d2)
{
//All cases when true should be returned
if (d1.year <d2.year)
return true ;
if (d1.year == d2.year && d1.month <d2.month)
return true ;
if (d1.year == d2.year && d1.month == d2.month &&
d1.day <d2.day)
return true ;

//If none of the above cases satisfy, return false
return false ;
}

//Function to sort array arr[0..n-1] of dates
void sortDates(Date arr[], int n)
{
//Calling in-built sort function.
//First parameter array beginning, //Second parameter - array ending, //Third is the custom compare function
sort(arr, arr+n, compare);
}

//Driver Program
int main()
{
Date arr[] = {{20, 1, 2014}, {25, 3, 2010}, { 3, 12, 1676}, {18, 11, 1982}, {19, 4, 2015}, { 9, 7, 2015}};
int n = sizeof (arr)/sizeof (arr[0]);

sortDates(arr, n);

cout <<"Sorted dates are\n" ;
for ( int i=0; i<n; i++)
{
cout <<arr[i].day <<" " <<arr[i].month
<<" " <<arr[i].year;
cout <<endl;
}
}``````

``````Sorted dates are
3 12 1676
18 11 1982
25 3 2010
20 1 2014
19 4 2015
9 7 2015``````

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