Книга: Standard Template Library Programmer

rotate

rotate

Category: algorithms

Component type: function

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

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).

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

• ForwardIterator is a model of Forward Iterator.

• ForwardIterator is mutable.

• [first, middle) is a valid range.

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

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

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

[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 Forward Iterators, Bidirectional Iterators, or Random Access Iterators. All three algorithms, however, are linear.

rotate_copy

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