rotate


function template
<algorithm>
template <class ForwardIterator>
  void rotate ( ForwardIterator first, ForwardIterator middle,
                ForwardIterator last );

Rotate elements in range

Rotates the order of the elements in the range [first,last), in such a way that the element pointed by middle becomes the new first element.

The behavior of this function template is equivalent to:
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template <class ForwardIterator>
  void rotate ( ForwardIterator first, ForwardIterator middle,
                ForwardIterator last )
{
  ForwardIterator next = middle;
  while (first!=next)
  {
    swap (*first++,*next++);
    if (next==last) next=middle;
    else if (first == middle) middle=next;
  }
}


Parameters

first, last
Forward iterators to the initial and final positions of the sequence to be rotated. 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.
Notice that in this function these are not consecutive parameters, but the first and the third.
middle
Forward iterator pointing to the element within the range [first,last) that is moved to the first position in the range.


Return value

none

Example

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// rotate algorithm 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<10; ++i) myvector.push_back(i); // 1 2 3 4 5 6 7 8 9

  rotate(myvector.begin(),myvector.begin()+3,myvector.end());
                                                  // 4 5 6 7 8 9 1 2 3

  // print out content:
  cout << "myvector contains:";
  for (it=myvector.begin(); it!=myvector.end(); ++it)
    cout << " " << *it;

  cout << endl;

  return 0;
}


Output:
myvector contains: 4 5 6 7 8 9 1 2 3


Complexity

At most, as many calls to swap as the length of the range [first,last).

See also

rotate_copy Copy rotated range (function template)
reverse Reverse range (function template)
random_shuffle Rearrange elements in range randomly (function template)
swap Exchange values of two objects (function template)