How to Access a Value in a Map Using a Key in C++?

In C++, maps are associative containers that store elements where each element has a key value and a mapped value. No two mapped values can have the same key values. In this article, we will learn how to access a value in a map using a key in C++ STL.

Example:

Input:      
myMap {'a' : 1,' b' : 2, 'c' : 3, 'd' : 4}
key=a
Output:

Value at key a is 1

Get a Value From Map Using a Key in C++

To access a value in a map using its key, we can use the [] array subscript operator of the map container to reference the element mapped to the key value given as the parameter.

C++ Program to Access a Value in a Map Using a Key

The below example demonstrates how to access value in a map in C++:

C++

// C++ Program to illustrate how to access a value in a map
// using a key
#include <iostream>
#include <map>
#include <string>
using namespace std;

int main()
{
    // map declaration
    map<string, int> mymap;

    // mapping strings to integers
    mymap["geeksforgeeks"] = 1;
    mymap["computer"] = 2;
    mymap["science"] = 3;
    mymap["portal"] = 4;

    // accessing the value in a map using key
    string key = "computer";
    cout << "Value at Key " << key
         << " is: " << mymap.at("computer");
    return 0;
}

Output

Value at Key computer is: 2

Time Complexity: O(log N)
Auxilliary Space: O(1)