# C++ Algorithm Library - copy_backward() Function

## Description

The C++ function std::algorithm::copy_backward() copies a range of elements to a new location in backward order.

## Declaration

Following is the declaration for std::algorithm::copy_backward() function form std::algorithm header.

### C++98

```template <class BidirectionalIterator1, class BidirectionalIterator2>
BidirectionalIterator2 copy_backward(BidirectionalIterator1 first,
BidirectionalIterator1 last, BidirectionalIterator2 result);
```

## Parameters

• first − Bidirectional iterators to the initial positions in a sequence.

• last − Bidirectional iterators to the final positions in a sequence.

• result − Bidirectional iterator to the past-the-end position in the destination sequence.

## Return value

Returns an iterator to the first element of the destination sequence where elements have been copied.

## Exceptions

Throws an exception if either element assignment or an operation on an iterator throws exception.

Please note that invalid parameters cause undefined behavior.

## Time complexity

Linear in the distance between first to last.

## Example

The following example shows the usage of std::algorithm::copy_backward() function.

```#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(void) {
vector<int> v1 = {1, 2, 3, 4, 5};
vector<int> v2(5);

copy_backward(v1.begin(), v1.end(), v2.end());

cout << "Vector v2 contains following elements" << endl;

for (auto it = v2.begin(); it != v2.end(); ++it)
cout << *it << endl;

return 0;
}
```

Let us compile and run the above program, this will produce the following result −

```Vector v2 contains following elements
1
2
3
4
5
```
algorithm.htm