How to Traverse a Map Using Iterator in C++?

In C++, maps are associative containers that store elements where each element has a key value and a mapped value. An iterator is a pointer-like object that allows traversing through the elements of a container like a map. In this article, we will learn how to traverse a map using an iterator in C++.

Example :

Input:
myMap[1] = "One";
myMap[2] = "Two";
myMap[3] = "Three";
myMap[4] = "Four";

Output:
Here is the map : {
 {1, One},
 {2, Two},
 {3, Three},
 {4, Four} }

Traverse a Map Using Iterator in C++

To traverse a std::map using an iterator, we can use the std::map::begin() function to get an iterator pointing to the first element of the map and the std::map::end() function to get an iterator pointing one past the last element of the map. Then we can increment the iterator in a loop to traverse through the elements.

C++ Program to Traverse a Map Using an Iterator

C++

// C++ Program to illustrate how to use iterator to traverse
// a map
#include <iostream>
#include <map>
using namespace std;

int main()
{
    // Create a map with some key-value pairs
    map<int, string> myMap;
    myMap[1] = "One";
    myMap[2] = "Two";
    myMap[3] = "Three";
    myMap[4] = "Four";
    myMap[5] = "Five";

    // Using iterator to traverse the map
    map<int, string>::iterator it;
    cout << "Here is the map : {" << endl;

    // using begin() and end() iterator to iterate
    // through the map
    for (it = myMap.begin(); it != myMap.end(); ++it) {
        cout << " {" << it->first << ", " << it->second
             << "} " << endl;
    }
    cout << '}' << endl;
    cout << "One full iteration complete.";

    return 0;
}

Output

Here is the map : {
 {1, One} 
 {2, Two} 
 {3, Three} 
 {4, Four} 
 {5, Five} 
}
One full iteration complete.

Time Complexity: O(n), where n is the number of elements in the map.
Auxiliary Space: O(1)