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set::erase() function in C++ STL

C++ STL set::erase() function: Here, we are going to learn about the erase() function of set in C++ STL (Standard Template Library).
Submitted by Radib Kar, on February 16, 2019

C++ STL set::erase() function

set::erase() function is a predefined function, it is used to erase an element from a set.

The function is used to erase an element based on its value or iterator position from the set.

Syntax

set<T> st; //declaration
set<T>::iterator it; //iterator declaration
st.erase( const T item); //prototype 1
//or
st.erase(iterator position) //prototype 2

Parameter(s)

const T item;  //prototype 1
Or
Iterator position //prototype 2

Return value

size_type //prototype 1
Or
void //prototype 2

Sample Input and Output

For a set of integer,
set<int> st;
set<int>::iterator it;
st.insert(4);
st.insert(5);
set content:
    4
    5

st.erase(4);  
set content:
    5

st.erase(st.begin()); //erases 5
set content:
empty set

Header file

Header file to be included:

#include <iostream>
#include <set>
OR
#include <bits/stdc++.h>

Example

#include <bits/stdc++.h>
using namespace std;

void printSet(set<int> st) {
  set<int>::iterator it;
  cout << "Set contents are:\n";
  for (it = st.begin(); it != st.end(); it++) cout << *it << " ";
  cout << endl;
}

int main() {
  cout << "Example of erase function\n";
  set<int> st;
  set<int>::iterator it;
  cout << "inserting 4\n";
  st.insert(4);
  cout << "inserting 6\n";
  st.insert(6);
  cout << "inserting 10\n";
  st.insert(10);

  printSet(st);  // printing current set

  cout << "erasing 6..\n";
  st.erase(6);  // prototype 1
  cout << "After erasing 6...\n";
  printSet(st);
  cout << "erasing first element of the set now\n";
  st.erase(st.begin());  // prototype 2
  cout << "after erasing first element of set now\n";

  printSet(st);

  return 0;
}

Output

Example of erase function
inserting 4
inserting 6
inserting 10
Set contents are:
4 6 10     
erasing 6..
After erasing 6...        
Set contents are:
4 10       
erasing first element of the set now    
after erasing first element of set now  
Set contents are:
10