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PAIR Template in STL

NOTE: Although Pair and Tuple are not actually the part of container library but we'll still discuss them as they are very commonly required in programming competitions and they make certain things very easy to implement.

SYNTAX of pair is:

pair<T1,T2>  pair1, pair2 ;

The above code creates two pairs, namely pair1 and pair2, both having first object of type T1 and second object of type T2.

Now T1 will be referred as first and T2 will be referred as second member of pair1 and pair2.

Example of Pair


Pair Template: Some Commonly used Functions

Here are some function for pair template :

  • Operator = : assign values to a pair.
  • swap : swaps the contents of the pair.
  • make_pair() : create and returns a pair having objects defined by parameter list.
  • Operators( == , != , > , < , <= , >= ) : lexicographically compares two pairs.

  • Program demonstrating PAIR Template

    #include <iostream>
    
    using namespace std;    
        
    int main ()
    {
       pair<int,int> pair1, pair3;    //creats pair of integers
       pair<int,string> pair2;    // creates pair of an integer an a string
        
       pair1 = make_pair(1, 2);     // insert 1 and 2 to the pair1
       pair2 = make_pair(1, "Studytonight") // insert 1 and "Studytonight" in pair2
       pair3 = make_pair(2, 4)
       cout<< pair1.first << endl;  // prints 1, 1 being 1st element of pair1
       cout<< pair2.second << endl; // prints Studytonight
    
       if(pair1 == pair3)
            cout<< "Pairs are equal" << endl;
       else
            cout<< "Pairs are not equal" << endl;
       
       return 0;
    }