Different Ways to Insert Elements in Set in C++ STL

Prerequisites:

• Set in C++ 

The C++ Standard Template Library offers containers called Sets. It functions essentially in the same ways as a binary search tree and is used to store different elements in increasing/decreasing order.

There are different methods to insert elements in the set as mentioned below:

• Adding one element to set
• Inserting an Iterator Range into a Set
• Inserting an Initializer List in the Set

1. Adding one element to set

The basic way to add an element is a set is to use an insert() function where the value of the element is passed as a parameter to this function.

Syntax:

set_name.insert(element)

// C++ program for inserting
// Elements In set
// one by one
#include <bits/stdc++.h>
using namespace std;

int main()
{
    // Create an empty set
    set<int> s;

    // Adding values to the set
    s.insert(10);
    s.insert(20);
    s.insert(30);

    // Printing the set
    for (int x : s) {
        cout << x << " ";
    }

    return 0;
}

10 20 30 

Time Complexity : O(log n)
Auxiliary Space : O(n)

2. Inserting an Iterator Range into a Set

We can insert any other container elements into sets using iterators. In order to insert a range of elements from another container 2 parameters are required which are basically iterators pointing to starting and ending elements of that range.

Syntax:

set_name.insert(Iterator starting, Iterator ending);

// C++ program to Insert
// Elements In set using
// Iterator Range
#include <bits/stdc++.h>
using namespace std;

int main()
{
    vector<int> v{ 10, 20, 30 };
    // Create an empty set
    set<int> s;

    // Inserting values of vector to set
    s.insert(v.begin(), v.end());

    // Printing the set
    for (int x : s) {
        cout << x << " ";
    }

    return 0;
}

10 20 30 

3. Inserting an Initializer List in Set

One more way to add the elements to a set is by inserting all elements from a list into the set. Given below is the syntax for this approach.

Syntax:

set_name.insert({element1,element2,element3,element4});

// C++ program for inserting
// Elements in set using
// Initializer List
#include <bits/stdc++.h>
using namespace std;

int main()
{
    // Create an empty set
    set<int> s;

    // Inserting all elements of the list
    // As we are inserting into set so the 
    // duplicate elements are rejected
    // and only one occurrence is considered.
    s.insert({10, 20, 30, 20, 10});
    
    // Printing the set
    for (int x : s)
        cout << x << " ";

    return 0;
}

10 20 30