How to sort an array of dates in C/C++?
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.
Related Problem:
How to efficiently sort a big list dates in 20’s
This article is contributed by Dinesh T.P.D.
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