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Queue of Pairs in C++ STL with Examples
  • Difficulty Level : Easy
  • Last Updated : 07 Apr, 2020
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Queue in STL are a type of container adaptors which operate in a first in first out (FIFO) type of arrangement where elements are inserted at the back (end) and are deleted from the front. Queue of pair can be very efficient in designing complex data structures. The first element is referenced as ‘first’ and the second element as ‘second’ and the order is fixed (first, second).

Syntax:

Queue<pair<datatype, datatype>> queue_of_pair;

Below are the images to show the working of Queue of Pairs:



Below is an example to show the Queue of Pairs:




// C++ program to demonstrate
// the working of STL queue of pairs
  
#include <bits/stdc++.h>
using namespace std;
  
// Print the current pair
void printPair(pair<int, int> p)
{
    // Gives first element from queue pair
    int f = p.first;
  
    // Gives second element from queue pair
    int s = p.second;
  
    cout << "(" << f << ", " << s << ") ";
}
  
// Print the Queue of Pairs
void showQueue(queue<pair<int, int> > gq)
{
    // Print element untill the
    // queue is not empty
    while (!gq.empty()) {
        printPair(gq.front());
        gq.pop();
    }
  
    cout << '\n';
}
  
// Driver code
int main()
{
    queue<pair<int, int> > gq;
  
    // Pushing elements inside
    // the queue container
    gq.push({ 10, 20 });
    gq.push({ 15, 5 });
    gq.push({ 1, 5 });
    gq.push({ 5, 10 });
    gq.push({ 7, 9 });
  
    cout << "Queue of Pairs: ";
    showQueue(gq);
  
    // Prints size of queue
    cout
        << "\nSize of Queue of Pairs: "
        << gq.size();
  
    // Prints first element
    // of queue container
    cout << "\nFront of Queue of Pairs: ";
    printPair(gq.front());
  
    // Prints last element
    // of queue container
    cout << "\nBack of Queue of Pairs: ";
    printPair(gq.back());
  
    cout << "\n\nRemoving the Front pair\n";
    gq.pop();
    cout << "Current Queue of Pairs: ";
    showQueue(gq);
  
    return 0;
}
Output:
Queue of Pairs: (10, 20) (15, 5) (1, 5) (5, 10) (7, 9) 

Size of Queue of Pairs: 5
Front of Queue of Pairs: (10, 20) 
Back of Queue of Pairs: (7, 9) 

Removing the Front pair
Current Queue of Pairs: (15, 5) (1, 5) (5, 10) (7, 9)

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