Codility 'CyclicRotation' Solution

Martin Kysel · January 19, 2016

Short Problem Definition:

Rotate an array to the right by a given number of steps.

Cyclic Rotation


expected worst-case time complexity is O(N)


There are multiple solutions to this problem. I picked the one that does not create a copy of the array.


def reverse(arr, i, j):
    for idx in xrange((j - i + 1) / 2):
        arr[i+idx], arr[j-idx] = arr[j-idx], arr[i+idx]

def solution(A, K):
    l = len(A)
    if l == 0:
        return []
    K = K%l
    reverse(A, l - K, l -1)
    reverse(A, 0, l - K -1)
    reverse(A, 0, l - 1)

    return A

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