How to Delete Multiple Key-Value Pairs from a Map in C++?

In C++, a map container stores the collection of data in the form of a key and a value pair and this data is sorted on the basis of the key. In this article, we will learn how to delete multiple key-value pairs from a map in C++ STL.

Example:

Input: 
myMap = {{“apple”, 1}, {“banana”, 2}, {“cherry”, 3}}; 
Delete the key-value pairs {“apple”, 1}, {“cherry”, 3}

Output: 
res={{"banana" : 2}}

Deleting Multiple Key-Value Pairs from Map in C++

If we want to delete multiple key-value pairs from a std::map, we can store the keys in the vector and then iterate the vector and keep deleting the keys using the std::map::erase() function.

C++ Program to Delete Multiple Key-Value Pairs from Map

C++

// C++ Program to illustrate how to delete multiple
// key-value pairs from a map
#include <iostream>
#include <map>
#include <vector>
using namespace std;

int main()
{
    // Creating a map of string and int
    map<string, int> myMap = { { "apple", 1 },
                               { "banana", 2 },
                               { "cherry", 3 } };

    // keys do be deleted
    vector<string> del({ "apple", "cherry" });

    // deleting elements
    for (auto key : del) {
        myMap.erase(key);
    }

    // Displaying the map elements
    for (auto it = myMap.begin(); it != myMap.end(); ++it) {
        cout << it->first << " " << it->second << endl;
    }

    return 0;
}

Output

banana 2

Time Complexity: O(M log N), where M is the number of elements to be deleted and N is the size of map.
Space Complexity: O(M)