Algorithm to rotate an array in linear time

Question

How to rotate an integer array by i times using swap function only in linear time.

Answer 1

An O(1) method of accomplishing this, in python:

class OffsetList(list):
    __slots__ = 'offset'
    def __init__(self, init=[], offset=-1):
        super(OffsetList, self).__init__(init)
        self.offset = offset
    def __getitem__(self, key):
        return super(OffsetList, self).__getitem__(key + self.offset)
    def __setitem__(self, key, value):
        return super(OffsetList, self).__setitem__(key + self.offset, value)
    def __delitem__(self, key):
        return super(OffsetList, self).__delitem__(key + self.offset)
    def index(self, *args):
        return super(OffsetList, self).index(*args) - self.offset

This is based on this answer about using a 1-based list in python.

This does have the slight glitch that if you attempt to index an item off the end of the list, it will return items from the (new) beginning, and negative indicies less than the size minus the offset won't work.