std::reverse
From cppreference.com
Defined in header <algorithm>
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(1) | ||
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 trueParameters
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.
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Return value
(none)
Exceptions
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 otherExecutionPolicy
, 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); } } |
Complexity
Exactly (last - first)/2
swaps.
Example
Run this code
#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; }
Output:
321 7654
See also
creates a copy of a range that is reversed (function template) |