multimap::erase() is a built-in function in C++ STL which is used to erase element from the container. It can be used to erase keys, elements at any specified position or a given range.
1. Syntax for erasing a key:

   multimap_name.erase(key)
   

   Parameters: The function accepts one mandatory parameter key which specifies the key to be erased in the multimap container.

   Return Value: The function does not return anything. It erases all the elements with the specified key.

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   // C++ program to illustrate // multimap::erase(key) #include <bits/stdc++.h> using namespace std;    int main() {        // initialize container     multimap<int, int> mp;        // insert elements in random order     mp.insert({ 2, 30 });     mp.insert({ 1, 40 });     mp.insert({ 3, 60 });     mp.insert({ 2, 20 });     mp.insert({ 5, 50 });        // prints the elements     cout << "The multimap before using erase() is : \n";     cout << "KEY\tELEMENT\n";     for (auto itr = mp.begin(); itr != mp.end(); ++itr) {         cout << itr->first              << '\t' << itr->second << '\n';     }        // function to erase given keys     mp.erase(1);     mp.erase(2);        // prints the elements     cout << "\nThe multimap after applying erase() is : \n";     cout << "KEY\tELEMENT\n";     for (auto itr = mp.crbegin(); itr != mp.crend(); ++itr) {         cout << itr->first              << '\t' << itr->second << '\n';     }     return 0; }

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   Output:

   The multimap before using erase() is : 
   KEY    ELEMENT
   1    40
   2    30
   2    20
   3    60
   5    50
   
   The multimap after applying erase() is : 
   KEY    ELEMENT
   5    50
   3    60
   

2. Syntax for removing a position:

   multimap_name.erase(iterator position)
   

   Parameters: The function accept one mandatory parameter position which specifies the iterator that is the reference to the position of the element to be erased.

   
   
   
   

   Return Value: The function does not returns anything.

   Program below illustrate the above syntax:

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   // C++ program to illustrate // multimap::erase(position) #include <bits/stdc++.h> using namespace std;    int main() {        // initialize container     multimap<int, int> mp;     // insert elements in random order     mp.insert({ 2, 30 });     mp.insert({ 1, 40 });     mp.insert({ 3, 60 });     mp.insert({ 2, 20 });     mp.insert({ 5, 50 });        // prints the elements     cout << "The multimap before using erase() is : \n";     cout << "KEY\tELEMENT\n";     for (auto itr = mp.begin(); itr != mp.end(); ++itr) {         cout << itr->first              << '\t' << itr->second << '\n';     }        // function to erase given position     auto it = mp.find(2);     mp.erase(it);        auto it1 = mp.find(5);     mp.erase(it1);        // prints the elements     cout << "\nThe multimap after applying erase() is : \n";     cout << "KEY\tELEMENT\n";     for (auto itr = mp.crbegin(); itr != mp.crend(); ++itr) {         cout << itr->first              << '\t' << itr->second << '\n';     }     return 0; }

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   Output:

   The multimap before using erase() is : 
   KEY    ELEMENT
   1    40
   2    30
   2    20
   3    60
   5    50
   
   The multimap after applying erase() is : 
   KEY    ELEMENT
   3    60
   2    20
   1    40
   

3. Syntax for erasing a given range:

   multimap_name.erase(iterator position1, iterator position2)
   

   Parameters: The function accepts two mandatory parameters which are described below:

   • position1 – specifies the iterator that is the reference to the element from which removal is to be done.
   • position2 – specifies the iterator that is the reference to the element upto which removal is to be done.

   Return Value: The function does not returns anything. It removes all the elements in the given range of iterators.

   Program below illustrate the above syntax:

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   // C++ program to illustrate // multimap::erase() #include <bits/stdc++.h> using namespace std;    int main() {        // initialize container     multimap<int, int> mp;     // insert elements in random order     mp.insert({ 2, 30 });     mp.insert({ 1, 40 });     mp.insert({ 3, 60 });     mp.insert({ 2, 20 });     mp.insert({ 5, 50 });        // prints the elements     cout << "The multimap before using erase() is : \n";     cout << "KEY\tELEMENT\n";     for (auto itr = mp.begin(); itr != mp.end(); ++itr) {         cout << itr->first              << '\t' << itr->second << '\n';     }        // function to erase in a given range     // find() returns the iterator reference to     // the position where the element is     auto it1 = mp.find(2);     auto it2 = mp.find(5);     mp.erase(it1, it2);        // prints the elements     cout << "\nThe multimap after applying erase() is : \n";     cout << "KEY\tELEMENT\n";     for (auto itr = mp.crbegin(); itr != mp.crend(); ++itr) {         cout << itr->first              << '\t' << itr->second << '\n';     }     return 0; }

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   Output:

   The multimap before using erase() is : 
   KEY    ELEMENT
   1    40
   2    30
   2    20
   3    60
   5    50
   
   The multimap after applying erase() is : 
   KEY    ELEMENT
   5    50
   1    40
   

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