Difference between revisions of "cpp/algorithm/reverse"
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Revision as of 21:19, 26 January 2017
| Defined in header <algorithm>
|
||
| template< class BidirIt > void reverse( BidirIt first, BidirIt last ); |
(1) | |
| 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)/22) 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 trueContents |
Parameters
| first, last | - | the range of elements to reverse |
| policy | - | the execution policy to use. See execution policy for details. |
| Type requirements | ||
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
ExecutionPolicyis 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
template<class BidirIt> void reverse(BidirIt first, BidirIt last) { while ((first != last) && (first != --last)) { std::iter_swap(first++, last); } } |
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)); std::cout << v[0] << v[1] << v[2] << '\n'; int a[] = {4, 5, 6, 7}; std::reverse(std::begin(a), std::end(a)); std::cout << a[0] << a[1] << a[2] << a[3] << '\n'; }
Output:
321 7654
Complexity
linear in the distance between first and last
See also
| creates a copy of a range that is reversed (function template) |
