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How to Reverse Iterate a Vector in C++?

Last Updated : 19 Nov, 2024
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In this article, we will learn different methods to iterate through the vector in reverse order in C++.

The most efficient method to iterate through the vector in reverse order is by using reverse iterator. Let’s take a look at an example:

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

int main() {
    vector<int> v = {1, 3, 4, 7, 9};

    // Iterating the vector in reverse order
    for (auto i = v.rbegin(); i != v.rend(); i++)
        cout << *i << " ";
  
    return 0;
}

Output
9 7 4 3 1

Explanation: We used reverse iteratorvector rbegin()and vector rend(). By iterating from rbegin() to rend(), we can print the elements of vector in reverse order.

There are also some other methods in C++ to iterate through the vector in reverse order. Some of them are as follows:

Table of Content

Using Index

A vector can be traverse in reverse order using for loop by starting from the last index and decrementing the index until we reach the first element.

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

int main() {
    vector<int> v = {1, 3, 4, 7, 9};

    // Iterating vector in reverse order
    for (int i = v.size() - 1; i >= 0; i--)
        cout << v[i] << " ";
  
    return 0;
}

Output
9 7 4 3 1

Using a Temporary Reversed Vector

Create a temporary reversed vector using reverse iterator and then traverse it using range-based loop.

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

int main() {
    vector<int> v = {1, 3, 4, 7, 9};

    // Iterating the vector in reverse order
    for (auto &i : vector<int>(v.rbegin(), v.rend()))
        cout << i << " ";
    return 0;
}

Output
9 7 4 3 1

Using reverse()

Reverse the vector using reverse() function, traverse the vector normally and reverse the vector again after traversal.

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

int main() {
    vector<int> v = {1, 3, 4, 7, 9};

    // reverse the vector
    reverse(v.begin(), v.end());

    // Iterating through vector
    for (auto i : v)
        cout << i << " ";
    return 0;
}

Output
9 7 4 3 1

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