How to Convert a Vector of Pairs to a Map in C++?

In C++, a vector of pairs can be converted to a map. This can be useful when you want to create a map from a vector of pairs, where each pair contains a key and a value. In this article, we will learn how to convert a vector of pairs to a map in C++.

For Example,

Input:
myVector = {{1, “one”}, {2, “two”}, {3, “three”}};
Output:
Map is : {1: “one”, 2 : “two”, 3 : “three”}

Vector of Pairs to Map in C++

To convert a std::vector of std::pair to std::map, we can use the range constructor of std::map that takes two iterators, one pointing to the beginning and the other to the end of the vector.

C++ Program to Convert a Vector of Pairs to a Map

The below example demonstrates how we can create a map of vectors and insert the key-value pairs in it in C++.

// C++ Program to illustrate how to Create a Map of Vectors
// Using Vector
#include <iostream>
#include <map>
#include <vector>
using namespace std;

int main()
{
    // Creating a vector of pairs
    vector<pair<int, string> > vec
        = { { 1, "one" }, { 2, "two" }, { 3, "three" } };

    // Converting the vector of pairs to a map
    map<int, string> myMap(vec.begin(), vec.end());

    // Printing the map
    for (auto& pair : myMap) {
        cout << pair.first << " => " << pair.second << endl;
    }

    return 0;
}

1 => one
2 => two
3 => three

Time Complexity: O(N logN), where N is the size of vector.
Auxiliary Space: O(N)