How to Traverse a Set with const_iterator in C++?

In C++, sets are a type of associative container in which each element has to be unique because the value of the element identifies it. It contains a constant iterator that provides the constant reference to its elements. In this article, we will discuss how to traverse a set with const_iterator in C++ STL.

Example

Input: 
input_set = {70,10,50,90,60,40,100,30,20,80}

Output:
10, 20, 30, 40, 50, 60, 70, 80, 90, 100

Traverse a Set with const_iterator in C++

const_iterator provides a constant reference to the container elements. It means that we can only access the value but cannot modify it. It is useful to prevent unintended changes that may occur while traversing.

The std::set class contains 4 functions that return the constant iterators:

• std::set::cbegin(): Return a const iterator that points to the first element of the set.
• std::set::cend(): Return a const iterator that points just after the last element of the set.
• std::set::crbegin(): Return a const reverse iterator that points to the reverse first element (last element) of the set.
• std::set::crend(): Return a const reverse iterator that points just after the reverse last element(first element) of the set.

We can use the above function to get the constant iterators and traverse the set using loops.

C++ Program to Traverse a Set with const_iterator

C++

// C++ program to traverse the set using the const_iterator.
#include <iostream>
#include <set>
using namespace std;

// Function to display elements of the set
// using rthe const_iterator
void display(set<int> set1)
{
    set<int>::const_iterator c_itr;
    for (c_itr = set1.cbegin(); c_itr != set1.cend();
         c_itr++) {
        cout << *c_itr << ", ";
    }
}

// Driver Code
int main()
{

    // Create an empty set
    set<int> set1;

    // Insert 10 elements into the set
    set1.insert(70);
    set1.insert(10);
    set1.insert(50);
    set1.insert(90);
    set1.insert(60);
    set1.insert(40);
    set1.insert(100);
    set1.insert(30);
    set1.insert(20);
    set1.insert(80);

    // Call the display() function
    display(set1);
    return 0;
}

Output

10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 

Time complexity: O(N), where N is the number of elements in the set.
Auxiliary Space: O(1)