C++ Custom Sort Method for STL Pair Template Program

Hello Everyone!

In this tutorial, we will learn about creating a Custom Sort Method for sorting a Pair Template its implementation using a Vector in the C++ programming language.

To understand the basic functionality of the Pair Template, we will recommend you visit, C++ STL Pair Template, where we have explained this concept in detail from scratch.

For a better understanding of its implementation, refer to the well-commented C++ code given below.

Code:

#include <iostream>
#include <bits/stdc++.h>

using namespace std;

//Returns true if x is smaller than y
bool cmp(pair<int, int> x, pair<int, int> y)
{
    if (x.first != y.first)
        return x.first < y.first; //return the one with smaller first element
    else
        return x.second < y.second; //if first element is equal then return the one with smaller second element
}

int main()
{
    cout << "\n\nWelcome to Studytonight :-)\n\n\n";
    cout << " =====  Program to demonstrate Custom Sorting of a Pair Template, in CPP  ===== \n\n";

    cout << "\n\nDeclaring a Vector and Filling it with integers.\n\n";

    //create an empty vector of pair
    vector<pair<int, int>> v;

    //insert elements into the vector
    v.push_back(make_pair(1, 5));
    v.push_back(make_pair(1, 3));
    v.push_back(make_pair(2, 6));
    v.push_back(make_pair(2, 4));
    v.push_back(make_pair(5, 24));

    //prining the vector of pairs
    cout << "Printing the Vector or Pairs: \n";

    int n = v.size();

    //Printing the vector
    for (int i = 0; i < n; i++)
    {
        cout << "\nPair is: " << v[i].first << " and " << v[i].second; //accessing the pair elements
    }

    cout << "\n\n\n--- Calling the Custom Sort Method ---";
    //Sorting the vector in ascending order of the pair
    sort(v.begin(), v.end(), cmp);

    cout << "\n\nThe elements of the Vector after Sorting are:\n ";

    //prining the Sorted vector
    for (int i = 0; i < n; i++)
    {
        cout << "\nPair is: " << v[i].first << " and " << v[i].second; //accessing the pair elements
    }

    cout << "\n\n\n";

    return 0;
}

Output:

We hope that this post helped you develop a better understanding of the concept of the Pair Template and its implementation in CPP. For any query, feel free to reach out to us via the comments section down below.

Keep Learning : )