C++ Pair Container: A Comprehensive Guide

What is C++ pair?

The C++ pair container is a basic header container that holds two data elements or objects. The order is set, and it refers to the first element as "first." It refers to the second element as "second" (first, second).

A pair is a term that is used to combine two values that may or may not be of the same kind. The C++ pair allows you to store two disparate items as a single entity.

It is possible to select, save, and compare pairs. By default, the list of objects assigned in a map or hashmap is of type ‘pair,' with all ‘first' components being special keys for their ‘second' value objects.

To get to the components, you use the vector name, the dot operator, and the keyword first or second.

pair (data_type1, data_type2) Pair_name

Example

// CPP program to illustrate pair STL

#include <iostream>

#include <utility>

using namespace std;

int main()

{

            pair<int, char> PAIR1; 

            PAIR1.first = 100;

            PAIR1.second = 'G';

            cout << PAIR1.first << " ";

            cout << PAIR1.second << endl;

            return 0;

}

Output

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How Can You Initialize a C++ Pair? 

pair (data_type1, data_type2) Pair_name (value1, value2) ;

Different Ways to Initialise a Pair

pair  g1;     //default

pair  g2(1, 'a');  //initialized,  different data type

pair  g3(1, 10);   //initialized,  same data type

pair  g4(g3); //copy of g3

Example:

// CPP program to illustrate

// Initializing of pair STL

#include <iostream>

#include <utility>

using namespace std;

int main()

{

                pair<string, double> PAIR2("GeeksForGeeks", 1.23);

                cout << PAIR2.first << " ";

                cout << PAIR2.second << endl; 

                return 0;

}

Output

What Are the Different Types of Member Functions?

Make_pair

This template feature allows you to construct a value pair without having to directly write the forms.

Pair_name = make_pair (value1,value2);

Example

#include <iostream>

#include <utility>

using namespace std;

int main()

{

            pair <int, char> PAIR1 ;

            pair <string, double> PAIR2 ("GeeksForGeeks", 1.23) ;

            pair <string, double> PAIR3 ;

            PAIR1.first = 100;

            PAIR1.second = 'G' ;

            PAIR3 = make_pair ("GeeksForGeeks is Best",4.56);

            cout << PAIR1.first << " " ;

            cout << PAIR1.second << endl ;

            cout << PAIR2.first << " " ;

            cout << PAIR2.second << endl ;

            cout << PAIR3.first << " " ;

            cout << PAIR3.second << endl ;

            return 0;

}

Output:

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What Are the Different Types of Operators in C++?

You can also use operators for sets.

equal(=) adds a new object to a pair of objects.

Syntax: This assigns pr to the pair object's new text. The first value receives the first value of pr, while the second receives the second value of pr.

• With C++ pair, use the comparison (==) operator: The comparison operator measures the first and second values of two sets, say pair1 and pair2, to see whether pair1.first is equal to pair2.first or not, and whether pair1.second is equal to pair2.second or not.
• For pair, use the not equal (!=) operator: The!= operator compares the first values of two sets, say pair1 and pair2, i.e. if pair1 and pair2 are given, the!= operator compares the first values of those two pairs.
• Pair of logical( >=, = )operators: The =, > operators can also be used for pairs, such as pair1 and pair2. It just compares the first value of the pair and returns 0 or 1.
• P2p1 should return 0 for pairs like p1=(1,20) and p2=(1,10) (because it just compares the first variable and they are equal, so it can't be less), but this isn't the case. When the first element becomes equal when using the relational operators > or only, the pair compares the second element and returns 1 if it satisfies

Example

#include <iostream>

#include<utility>

using namespace std;

int main()

{

            pair<char, int>pair1 = make_pair('A', 1);

            pair<char, int>pair2 = make_pair('B', 2); 

            cout << "Before swapping:\n " ;

            cout << "Contents of pair1 = "

                           << pair1.first << " " << pair1.second ;

            cout << "Contents of pair2 = "

                           << pair2.first << " " << pair2.second ;

            pair1.swap(pair2);

             cout << "\nAfter swapping:\n ";

            cout << "Contents of pair1 = "

                           << pair1.first << " " << pair1.second ;

            cout << "Contents of pair2 = "

                           << pair2.first << " " << pair2.second ; 

            return 0;

} 

Output

Conclusion

This article pretty much sums up the C++ pair. For a full-fledged course in the subject, you must enroll in Simplilearn’s Post Graduate Program in Full Stack Development. Offered in collaboration with Caltech CTME. This comprehensive, globally-recognized applied learning program gives you everything you need to begin enjoying consisten and accelerated growth in your career graph as a full stack development professional anywhere in the world. For better understanding and getting hired by the best companies, you can also look for a course. 

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