std::copy_backward
From cppreference.com
Defined in header <algorithm>
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template< class BidirIt1, class BidirIt2 > BidirIt2 copy_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last ); |
(until C++20) | |
template< class BidirIt1, class BidirIt2 > constexpr BidirIt2 copy_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last ); |
(since C++20) | |
Copies the elements from the range, defined by [first, last)
, to another range ending at d_last
. The elements are copied in reverse order (the last element is copied first), but their relative order is preserved.
The behavior is undefined if d_last
is within (first, last]
. std::copy must be used instead of std::copy_backward
in that case.
Contents |
[edit] Parameters
first, last | - | the range of the elements to copy from |
d_last | - | the end of the destination range |
Type requirements | ||
-BidirIt must meet the requirements of LegacyBidirectionalIterator.
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[edit] Return value
iterator to the last element copied.
[edit] Complexity
Exactly last - first
assignments.
[edit] Notes
When copying overlapping ranges, std::copy
is appropriate when copying to the left (beginning of the destination range is outside the source range) while std::copy_backward
is appropriate when copying to the right (end of the destination range is outside the source range).
[edit] Possible implementation
template< class BidirIt1, class BidirIt2 > BidirIt2 copy_backward(BidirIt1 first, BidirIt1 last, BidirIt2 d_last) { while (first != last) *(--d_last) = *(--last); return d_last; } |
[edit] Example
Run this code
#include <algorithm> #include <iostream> #include <numeric> #include <vector> int main() { std::vector<int> source(4); std::iota(source.begin(), source.end(), 1); // fills with 1, 2, 3, 4 std::vector<int> destination(6); std::copy_backward(source.begin(), source.end(), destination.end()); std::cout << "destination contains: "; for (auto i: destination) std::cout << i << ' '; std::cout << '\n'; }
Output:
destination contains: 0 0 1 2 3 4
[edit] See also
(C++11) |
copies a range of elements to a new location (function template) |
(C++20) |
copies a range of elements in backwards order (niebloid) |