multimap::erase() in C++ STL (original) (raw)

Last Updated : 18 Nov, 2020

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. CPP `
   // 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;
}
**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: CPP
// 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;
}
`
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: CPP `
  // 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;
}
`

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