copy_backward
function template
<algorithm>
template <class BidirectionalIterator1, class BidirectionalIterator2>
BidirectionalIterator2 copy_backward ( BidirectionalIterator1 first,
BidirectionalIterator1 last,
BidirectionalIterator2 result );
Copy range of elements backwards
Copies the elements in the range [first,last) into a range whose last element is result. The function begins by copying *(last-1) into *(result-1), and then follows backwards by the elements preceeding these, until first is reached (and including it).
Returns an iterator to the first element in the destination range.
The behavior of this function template is equivalent to:
1
2
3
4
5
6
7
8
|
template<class BidirectionalIterator1, class BidirectionalIterator2>
BidirectionalIterator2 copy_backward ( BidirectionalIterator1 first,
BidirectionalIterator1 last,
BidirectionalIterator2 result )
{
while (last!=first) *(--result) = *(--last);
return result;
}
|
If both ranges overlap in such a way that result (which is the past-the-end element in the destination range) points to an element in the range [first,last), the function copy should be used instead.
Parameters
- first, last
- Binary iterators to the initial and final positions in a sequence to be copied. The range used is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
- result
- Binary iterator to the past-the-end position in the destination sequence. This shall not point to any element in the range [first,last).
Return value
An iterator to the first element of the destination sequence where elements have been copied.
Example
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
|
// copy_backward example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main () {
vector<int> myvector;
vector<int>::iterator it;
// set some values:
for (int i=1; i<=5; i++)
myvector.push_back(i*10); // myvector: 10 20 30 40 50
myvector.resize(myvector.size()+3); // allocate space for 3 more elements
copy_backward ( myvector.begin(), myvector.begin()+5, myvector.end() );
cout << "myvector contains:";
for (it=myvector.begin(); it!=myvector.end(); ++it)
cout << " " << *it;
cout << endl;
return 0;
}
|
Output:
myvector contains: 10 20 30 10 20 30 40 50 |
Complexity
Linear: Performs as many assignment operations as the distance between first and last.
See also
| copy | Copy range of elements (function template) |
| fill | Fill range with value (function template) |
| replace | Replace value in range (function template) |
|