Insertion and Deletion in STL Set C++ Program

In this tutorial, we will be discussing a program to understand the insertion and deletion in STL set in C++.

The set is a container element. The properties that make it unique is that it can only contain unique elements and they can be looped over in a sorted manner.

Example

Insertion

 Live Demo

#include<iostream>
#include<set>
using namespace std;
int main(){
   set<int> st;
   //declaring iterators
   set<int>::iterator it = st.begin();
   set<int>::iterator it1, it2;
   pair< set<int>::iterator,bool> ptr;
   //inserting a single element
   ptr = st.insert(20);
   if (ptr.second)
      cout << "The element was newly inserted" ;
   else cout << "The element was already present" ;
      cout << "\nThe set elements after 1st insertion are : ";
   for (it1 = st.begin(); it1!=st.end(); ++it1)
      cout << *it1 << " ";
   st.insert(it, 24);
   cout << "\nThe set elements after 2nd insertion are : ";
   for (it1 = st.begin(); it1!=st.end(); ++it1)
      cout << *it1 << " ";
   int arr[3] = { 25, 24, 26 };
   st.insert(arr, arr+3);
   cout << "\nThe set elements after 3rd insertion are : ";
   for (it1 = st.begin(); it1!=st.end(); ++it1)
      cout << *it1 << " ";
}

Output

The element was newly inserted
The set elements after 1st insertion are : 20
The set elements after 2nd insertion are : 20 24
The set elements after 3rd insertion are : 20 24 25 26

Deletion

 Live Demo

#include<iostream>
#include<set>
using namespace std;
int main(){
   set<int> st;
   //declaring iterators
   set<int>::iterator it;
   set<int>::iterator it1;
   set<int>::iterator it2;
   pair< set<int>::iterator,bool> ptr;
   //inserting values in set
   for (int i=1; i<10; i++)
      st.insert(i*5);
   cout << "The set elements after insertion are : ";
   for (it1 = st.begin(); it1!=st.end(); ++it1)
      cout << *it1 << " ";
   it = st.begin();
   cout << endl;
   ++it;
   st.erase(it);
   //printing set elements after deletion
   cout << "The set elements after 1st deletion are : ";
   for (it1 = st.begin(); it1!=st.end(); ++it1)
      cout << *it1 << " ";
   st.erase(40);
   cout << "\nThe set elements after 2nd deletion are : ";
   for (it1 = st.begin(); it1!=st.end(); ++it1)
      cout << *it1 << " ";
   ++it;
   ++it;
   ++it;
   ++it;
   st.erase(it, st.end());
   cout << "\nThe set elements after 3rd deletion are : ";
   for (it1 = st.begin(); it1!=st.end(); ++it1)
      cout << *it1 << " ";
   cout << endl;
}

Output

The set elements after insertion are : 5 10 15 20 25 30 35 40 45
The set elements after 1st deletion are : 5 15 20 25 30 35 40 45
The set elements after 2nd deletion are : 5 15 20 25 30 35 45
The set elements after 3rd deletion are : 5 15 20