std::reverse

 

C++

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Technical Specifications

 

Algorithm library

Functions
Non-modifying sequence operations
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each countcount_if mismatch equal	findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n removeremove_if remove_copyremove_copy_if	replacereplace_if replace_copyreplace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) unique unique_copy
Partitioning operations
is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
Sorting operations (on sorted ranges)
is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
Binary search operations (on sorted ranges)
lower_bound upper_bound	binary_search equal_range
Set operations (on sorted ranges)
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
Heap operations
is_heap (C++11) is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
Minimum/maximum operations
max max_element min min_element minmax (C++11) minmax_element (C++11)	lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
Numeric operations
iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

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

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::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

reverse_copy	creates a copy of a range that is reversed (function template)
std::experimental::parallel::reverse (parallelism TS)	parallelized version of std::reverse (function template)