How to sort an array of dates in C/C++?
Last Updated :
11 Sep, 2023
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Given an array of dates, how to sort them.
Example:
C
Output:
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;
}
}
// C++ program to sort an array of datesusing namespace std;// Structure for datestruct 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 datebool 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 datesvoid 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 Programint 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 2015Similarly in C, we can use qsort() function. Related Problem: How to efficiently sort a big list dates in 20’s This article is contributed by Dinesh T.P.D.
