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

Last Updated : 23 Jul, 2025
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In this article, we will learn how to replace an element in a vector in C++.

The most efficient method to replace the old value with a new value is by using replace() method. Let’s take a look at an example:

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

int main() {
    vector<int> v = {1, 3, 6, 2, 7, 2};

    // Replace all 2s with 22
    replace(v.begin(), v.end(), 2, 22);
  
    for (auto i : v)
        cout << i << " ";
    return 0;
}

Output
1 3 6 22 7 22

Explanation: The replace() method replace all the occurrences of the given element in the vector with the new value.

There are also some other method in C++ by which we can replace the given old values with new value. Some of them are as follows:

Using transform()

The transform() method allows us to apply a transformation (e.g., replacing elements) to all elements in the vector based on a transformation function.

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

int main() {
    vector<int> v = {1, 3, 6, 2, 7, 2};

    // Replacing all 2s in vector with 22
    transform(v.begin(), v.end(), v.begin(),
              [](int i) { 
                return i == 2 ? 22 : i;
              });
  
    for (auto i : v)
        cout << i << " ";
    return 0;
}

Output
1 3 6 22 7 22

Manually Using Loop

In this method, iterate through the vector using a loop and check the element at every index. If it is equal to given value, then assign it the new value.

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

int main() {
    vector<int> v = {1, 3, 6, 2, 7, 2};

    // Replacing all 2s in vector with 22
    for (auto &i : v) {
        if (i == 2)
            i = 22;
    }
  
    for (auto i : v)
        cout << i << " ";
    return 0;
}

Output
1 3 6 22 7 22



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