How to Use reverse in C++: Syntax and Examples

In C++, you can use the std::reverse function from the <algorithm> header to reverse elements in a container like an array or vector. Call it with two iterators marking the start and end of the range you want to reverse, for example, std::reverse(vec.begin(), vec.end()).

Syntax

The std::reverse function reverses the order of elements in a range defined by two iterators.

• first: Iterator to the beginning of the range.
• last: Iterator to one past the end of the range.

It modifies the container in place.

cpp

std::reverse(first, last);

Example

This example shows how to reverse a vector of integers using std::reverse. It prints the vector before and after reversing.

cpp

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    std::vector<int> numbers = {1, 2, 3, 4, 5};

    std::cout << "Before reverse: ";
    for (int n : numbers) std::cout << n << ' ';
    std::cout << '\n';

    std::reverse(numbers.begin(), numbers.end());

    std::cout << "After reverse: ";
    for (int n : numbers) std::cout << n << ' ';
    std::cout << '\n';

    return 0;
}

Output

Before reverse: 1 2 3 4 5 
After reverse: 5 4 3 2 1 

Common Pitfalls

Common mistakes when using std::reverse include:

• Passing invalid or reversed iterators (the first iterator must come before the last).
• Trying to reverse a container without including <algorithm>.
• Expecting std::reverse to return a new container; it modifies in place and returns void.

cpp

#include <vector>
#include <algorithm>

// Wrong: reversed iterators
// std::reverse(vec.end(), vec.begin()); // This causes undefined behavior

// Correct:
// std::reverse(vec.begin(), vec.end());

Quick Reference

• Include <algorithm> to use std::reverse.
• Use iterators to specify the range to reverse.
• Works with arrays, vectors, strings, and other containers supporting iterators.
• Modifies the container in place; no return value.

Key Takeaways

Use std::reverse from to reverse elements between two iterators.

Always pass the beginning iterator first, then the end iterator (one past last element).

std::reverse modifies the container in place and returns void.

Works with many containers like vectors, arrays, and strings.

Include header to access std::reverse.