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# copy_n

Copies a specified number of elements

## Definition

The copy_n() algorithm is defined in the standard header <algorithm> and in the nonstandard backward-compatibility header <algo.h>.

## Interface

```#include <algorithm>
template < class InputIterator, class Size, class OutputIterator >
OutputIterator copy_n(
InputIterator  first,
Size count,
OutputIterator result
);```

Parameters:
Parameter Description
first An input iterator that indicates where to copy elements from
count A signed or unsigned integer type specifying the number of elements to copy
result An output iterator that indicates where to copy elements to

## Description

Copy_n copies elements from the range `[first, first + n)` to the range `[result, result + n)`.

## Return Value

Returns an output iterator where elements have been copied to. It is the same as the returned value of the third parameter, `result`.

## Complexity

The complexity is linear, `n` assignments are performed.

### References

Example:

##### Example - copy_n algorithm
Problem
This example of program illustrates the functionality of copy_n() algorithm.
Workings
```#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>

int main()
{
std::string in = "1234567890";
std::string out;

std::copy_n(in.begin(), 4, std::back_inserter(out));
std::cout <<out <<'\n';

return 0;
}```
Solution
Output:

1234
References