Sortvector.Cpp

// C++ program to demonstrate sorting in vector
// of pair according to 2nd element of pair
#include<bits/stdc++.h>

using namespace std;
 
// Driver function to sort the vector elements
// by second element of pairs

bool sortbysec(const pair<int,int> &a,

              const pair<int,int> &b)
{

    return (a.second < b.second);
}
 

int main()
{

    // declaring vector of pairs

    vector< pair <int, int> > vect;
 

    // Initialising 1st and 2nd element of pairs

    // with array values

    int arr[] = {10, 20, 5, 40 };

    int arr1[] = {30, 60, 20, 50};

    int n = sizeof(arr)/sizeof(arr[0]);
 

    // Entering values in vector of pairs

    for (int i=0; i<n; i++)

        vect.push_back( make_pair(arr[i],arr1[i]) );
 

    // Printing the original vector(before sort())

    cout << "The vector before sort operation is:\n" ;

    for (int i=0; i<n; i++)

    {

        // "first" and "second" are used to access

        // 1st and 2nd element of pair respectively

        cout << vect[i].first << " "

             << vect[i].second << endl;
 

    }
 

    // Using sort() function to sort by 2nd element

    // of pair

    sort(vect.begin(), vect.end(), sortbysec);
 

    // Printing the sorted vector(after using sort())

    cout << "The vector after sort operation is:\n" ;

    for (int i=0; i<n; i++)

    {

        // "first" and "second" are used to access

        // 1st and 2nd element of pair respectively

        cout << vect[i].first << " "

             << vect[i].second << endl;

    }

    return 0;
}