How to Delete a Pair from a Multimap in C++?

Last Updated : 06 Feb, 2024

In C++, multimap stores key-value pairs and for the same key there can be multiple values in a multimap. In this article, we will learn how to delete a pair from a multimap in C++.

Example

Input:
mpp={{"apple", 1},{"banana", 2},{"apple", 3}, {"orange", 4}}
keyToRemove=apple
valueToRemove=3
Output:
apple: 1
banana: 2
orange: 4

Remove a Pair from Multimap in C++

To delete a pair from multimap, we can use the std::multimap::erase() function with a combination of std::find_if().

First, create a custom binary predicate function to pass to the find_if() function to check for the matching key-value pair and find the iterator using the find_if() function. Then remove the pair using erase() by passing the iterator in it.

C++ Program to Delete a Pair from Multimap

C++

// C++ program to delete a pair from multimap 
#include <algorithm> 
#include <iostream> 
#include <map> 
  
using namespace std; 
  
int main() 
{ 
  
    // creating a mutimap 
    multimap<string, int> myMpp = { 
        { "apple", 1 }, 
        { "banana", 2 }, 
        { "apple", 3 }, 
        { "orange", 4 }, 
    }; 
  
    // Define the key and value to remove 
    string keyToRemove = "apple"; 
    int valueToRemove = 3; 
  
    // Find the element 
    auto it = find_if( 
        myMpp.begin(), myMpp.end(), [&](const auto& pair) { 
            return pair.first == keyToRemove 
                   && pair.second == valueToRemove; 
        }); 
  
    // If found, erase it 
    if (it != myMpp.end()) { 
        myMpp.erase(it); 
    } 
  
    // Iterate and print remaining elements 
    for (const auto& pair : myMpp) { 
        cout << pair.first << ": " << pair.second << endl; 
    } 
  
    return 0; 
}

Output

apple: 1
banana: 2
orange: 4

Time Complexity: O(N)
Auxiliary Space: O(1)

Note: We can also use equal_range() with erase() function to delete a pair from multimap.

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

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