How to sort an array of dates in C/C++?

Last Updated : 11 Sep, 2023

Given an array of dates, how to sort them.

Example:

  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}}

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The idea is to use in-built function to sort function in C++. We can write our own compare function that first compares years, then months, then days.

Below is a complete C++ program.

   // 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; 
    } 
} 
 
  

Output:

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

Similarly in C, we can use qsort() function.

This article is contributed by Dinesh T.P.D.

Sorting Strings using Bubble Sort

Dinesh T

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How to sort an array of dates in C/C++?

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