ex-2-1-cyclicrotation.py

import unittest
import random

ARRAY_RANGE = (-1000, 1000)
INT_RANGE = (0, 100)


def solution(A, K):
    """
    Rotate the array A by k steps
    :param A: an array of integers
    :param K: number of times to shift right
    :return: the rotated array
    """
    # A is empty
    if not len(A):
        return A

    # netK is the net number of shifts to apply (omits spinning round and round)
    netK = (len(A) + K) % len(A)
    if netK > 0:
        head = A[len(A)-netK:]
        tail = A[:-netK]
        return head + tail
    else:
        return A


class TestCyclicRotation(unittest.TestCase):

    def test_zero(self):
        self.assertEqual(solution([6, 3, 8, 9, 7], 0), [6, 3, 8, 9, 7])

    def test_one(self):
        self.assertEqual(solution([6, 3, 8, 9, 7], 1), [7, 6, 3, 8, 9])

    def test_example1(self):
        self.assertEqual(solution([3, 8, 9, 7, 6], 3), [9, 7, 6, 3, 8])

    def test_full(self):
        self.assertEqual(solution([6, 3, 8, 9, 7], 5), [6, 3, 8, 9, 7])

    def test_empty(self):
        self.assertEqual(solution([], 5), [])

    def test_random(self):
        N = random.randint(*INT_RANGE)
        K = random.randint(*INT_RANGE)
        A = [random.randint(*ARRAY_RANGE) for i in xrange(0, N)]
        print N, K, A
        print solution(A, K)

if __name__ == '__main__':
    unittest.main()