Pair in STL C++
About Pair in STL :
std::pair is a template class provided by the STL that allows us to bundle two different data elements together into a single unit. This powerful feature is incredibly versatile and finds its applications in various programming scenarios. Whether you need to associate two variables, represent key-value pairs, or return multiple values from a function, std::pair comes to the rescue.
Creating and Initializing std::pair
To create a std::pair, we must include the <utility> header in our C++ code. Initializing a pair can be achieved using different methods, such as the `make_pair` function or the brace initialization syntax.Accessing Elements in a std::pair
Once we have a pair, we need to access its elements. This can be accomplished using the first and second member functions. Understanding how to access these elements is crucial for effectively utilizing std::pair.
Syntax of Pair :
pair< data_type, data_type> pair_name;
Pair is a container that is given by the “utility” library and is declared in C++ by using the keyword “pair”. In essence, a pair is used to combine two components or values into one, allowing for the storage of things with various data types or two heterogeneous objects as a single entity. Only two components can be stored in the pair container, the first of which can only be referred by “first” and the second of which can only be stored in “second”.
Functions in Pair :
| Function | Working |
|---|---|
| make_pair() | store two values in the pair. |
| swap() | swap the components of pair 1 and pair 2. |
| tie() | unpacks the pair values into independent variables |
Example of Pair in STL :
#include<iostream
#include<bits/stdc++.h>
using namespace std;
int main() {
pair<int, int> p1;
pair<string, int> p2("PrepInsta",1);
p1.first = 2;
p1.second = 3;
cout<<"The elements in pair p1 : ";
cout<< p1.first<<" "<< p1.second<< endl;
cout<<"The elements in pair p2: ";
cout<< p2.first<<" "<< p2.second;
return 0;
}
Output :
The elements in pair p1 : 2 3 The elements in pair p2: PrepInsta 1
In the above program, take two pair p1 and p2, insert value in pair p1 and p2, print them on the screen.
Example of Pair in STL:
#include<iostream>
#include<bits/stdc++.h>
using namespace std;
int main() {
pair p1;
pair p2(100,1);
p1 = make_pair(2,3); // function to insert value in pair
cout<<"The elements in pair p1 before swapping : ";
cout<< p1.first<< " "<< p1.second<< endl;
cout<<"The elements in pair p2: ";
cout<< p2.first<< " "<< p2.second<< endl;
p1.swap(p2); // swap function n pair
cout<<"The elements in pair p1 after swapping : ";
cout<< p1.first<< " " << p1.second;
return 0;
}
Output :
The elements in pair p1 before swapping : 2 3 The elements in pair p2: 100 1 The elements in pair p1 after swapping : 100 1
In the above program, take two pair p1 and p2, insert value in p2 by make_pair function while also use swap function swap the values of pair p2 and p1.
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