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std::reverse

From cppreference.com
< cpp‎ | algorithm
Revision as of 18:21, 12 September 2013 by Nate (Talk | contribs)

 
 
 
Defined in header <algorithm>
template< class BidirIt >
void reverse( BidirIt first, BidirIt last );

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

Contents

Parameters

first, last - the range of elements to reverse
Type requirements
-
BidirIt must meet the requirements of BidirectionalIterator.
-
The type of dereferenced BidirIt must meet the requirements of Swappable.

Return value

(none)

Possible implementation

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

Example

#include <vector>
#include <iostream>
#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(&a[0], &a[4]);
    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) [edit]