How to Replace an Element in a Deque in C++?

In C++, deque (short for double-ended queue) allows fast insertions and deletions at both its beginning and its end. In this article, we will learn how to replace a specific element in a deque in C++.

Example:

Input: 
myDeque:  {1, 2, 3, 4, 5, 3, 7}

Output:
// Replaced element 3 with 10
Updated Deque: 1 2 10 4 5 10 7

Replace an Element in a Deque in C++

To replace a specific element in a deque in C++, we can use the std::replace() method provided by the STL library. The replace method will replace all the occurrences of the specific element within the given range.

Syntax of std::replace()

replace(first, last, int target, int substitute)

where,

• first and last are iterators denoting the range of dequeue elements.
• target is the element you want to replace.
• substitute is the element you want to replace target element with.

C++ Program to Replace a Specific Element in a Deque

The below program demonstrates how we can replace a specific element in a deque in C++:

C++

// C++ Program to illustrate how to replace a specific
// element in a deque
#include <algorithm>
#include <deque>
#include <iostream>
using namespace std;

int main()
{
    // Initialize a deque
    deque<int> dq = { 1, 2, 3, 4, 5, 3, 7 };

    // Declare the target element
    int target = 3;

    // Declare the substitute element
    int substitute = 10;

    // Print the original deque
    cout << "Original Deque: ";
    for (int x : dq) {
        cout << x << " ";
    }
    cout << endl;
    // Replace the specific element in the deque
    replace(dq.begin(), dq.end(), target, substitute);

    // Print the updated deque
    cout << "Updated Deque: ";
    for (int x : dq) {
        cout << x << " ";
    }

    return 0;
}

Output

Original Deque: 1 2 3 4 5 3 7 
Updated Deque: 1 2 10 4 5 10 7 

Time Complexity: O(N) where N is the size of deque
Auxiliary Space: O(1)