< cpp‎ | algorithm
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Concepts and utilities: std::Sortable, std::projected, ...
Constrained algorithms: std::ranges::copy, std::ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
Binary search operations
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
Numeric operations
C library
Defined in header <algorithm>
template< class BidirIt >
void reverse( BidirIt first, BidirIt last );
(until C++20)
template< class BidirIt >
constexpr void reverse( BidirIt first, BidirIt last );
(since C++20)
template< class ExecutionPolicy, class BidirIt >
void reverse( ExecutionPolicy&& policy, BidirIt first, BidirIt last );
(2) (since C++17)
1) Reverses the order of the elements in the range [first, last)
Behaves as if applying std::iter_swap to every pair of iterators first+i, (last-i) - 1 for each non-negative i < (last-first)/2
2) Same as (1), but executed according to policy. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true


first, last - the range of elements to reverse
policy - the execution policy to use. See execution policy for details.
Type requirements
BidirIt must meet the requirements of ValueSwappable and LegacyBidirectionalIterator.

Return value



The overload with a template parameter named ExecutionPolicy reports errors as follows:

  • If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
  • If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

See also the implementations in libstdc++ and libc++.

template<class BidirIt>
void reverse(BidirIt first, BidirIt last)
    while ((first != last) && (first != --last)) {
        std::iter_swap(first++, last);


Exactly (last - first)/2 swaps.


#include <vector>
#include <iostream>
#include <iterator>
#include <algorithm>
int main()
    std::vector<int> v{1,2,3};
    std::reverse(std::begin(v), std::end(v));
    for(auto e : v) std::cout << e;
    std::cout << '\n';
    int a[] = {4, 5, 6, 7};
    std::reverse(std::begin(a), std::end(a));
    for(auto e : a) std::cout << e;



See also

creates a copy of a range that is reversed
(function template)