# rotate

 Category: algorithms Component type: function

## Prototype

```template <class ForwardIterator>
inline ForwardIterator rotate(ForwardIterator first, ForwardIterator middle,
ForwardIterator last);
```

## Description

`Rotate` rotates the elements in a range. That is, the element pointed to by `middle` is moved to the position `first`, the element pointed to by `middle + 1` is moved to the position `first + 1`, and so on. One way to think about this operation is that it exchanges the two ranges `[first, middle)` and `[middle, last)`. Formally, for every integer `n` such that `0 <= n < last - first`, the element `*(first + n)` is assigned to `*(first + (n + (last - middle)) % (last - first))`. `Rotate` returns `first + (last - middle)`.

## Definition

Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

## Requirements on types

• `ForwardIterator` is a model of ForwardIterator.
• `ForwardIterator` is mutable.

## Preconditions

• `[first, middle)` is a valid range.
• `[middle, last)` is a valid range. [1]

## Complexity

Linear. At most `last - first` swaps are performed. [2]

## Example

```char alpha[] = "abcdefghijklmnopqrstuvwxyz";
rotate(alpha, alpha + 13, alpha + 26);
printf("%s\n", alpha);
// The output is nopqrstuvwxyzabcdefghijklm
```

## Notes

[1] It follows from these two requirements that `[first, last)` is a valid range.

[2] `Rotate` uses a different algorithm depending on whether its arguments are ForwardIterator, BidirectionalIterator, or RandomAccessIterator. All three algorithms, however, are linear.

`rotate_copy`