How to Declare a Map in C++?

In C++, maps are associative containers that store elements in a mapped fashion. 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 declare a map in C++.

How to declare a map in C++?

In C++, you can declare a map using the std::map template class, which is part of the <map> header.

Syntax to declare a map in C++ STL

std::map<KeyType, ValueType> mapName;

where,

• KeyType: This is the data type of the keys in the map.
• ValueType: This is the data type of the values associated with the keys in the map.
• mapName: This is the name you give to your map variable.

C++ Program to Declare a Map

C++

// C++ Program to declare a map
#include <iostream>
#include <map>
#include <string>
using namespace std;

// Driver Code
int main()
{
    // Create a map of strings to integers
    map<string, int> mp;

    // Insert some values into the map
    mp["one"] = 1;
    mp["two"] = 2;
    mp["three"] = 3;

    // Get an iterator pointing to the first element in the
    // map
    map<string, int>::iterator it = mp.begin();

    // Iterate through the map and print the elements
    while (it != mp.end()) {
        cout << "Key: " << it->first
             << ", Value: " << it->second << endl;
        ++it;
    }

    return 0;
}

Output

Key: one, Value: 1
Key: three, Value: 3
Key: two, Value: 2