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

Suppose we have an array of dates. Here we will see how to sort then using C or C++ code. The dates are stored in a class (struct can be used in C also). We will use the sort function of the C++ STL. For comparing dates, we have to write our own compare function that will be used in the sort function. Let us see the example to get better view.

Example

#include<iostream>
#include<iostream>
#include<algorithm>
using namespace std;
class Date {
   public:
      int d, m, y;
};
bool compare(const Date &date1, const Date &date2){
   if (date1.y < date2.y)
      return true;
   if (date1.y == date2.y && date1.m < date2.m)
      return true;
   if (date1.y == date2.y && date1.m == date2.m && date1.d < date2.d)
      return true;
   return false;
}
void sortDateArray(Date arr[], int n) {
   sort(arr, arr+n, compare);
}
int main() {
   Date arr[] = {{20, 1, 2017},
   {25, 3, 2010},
   { 3, 12, 1956},
   {18, 10, 1982},
   {19, 4, 2011},
   { 9, 7, 2013}};
   int n = sizeof(arr)/sizeof(arr[0]);
   sortDateArray(arr, n);
   cout << "Sorted dates are" << endl;
   for (int i=0; i<n; i++) {
      cout << arr[i].d << " " << arr[i].m << " " << arr[i].y << endl;
   }
}

Output

Sorted dates are
3 12 1956
18 10 1982
25 3 2010
19 4 2011
9 7 2013
20 1 2017