algorithms/array/rotate_array.py at master · DaMacho/algorithms · GitHub

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"""

Rotate an array of n elements to the right by k steps.

For example, with n = 7 and k = 3,

the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].

Note:

Try to come up as many solutions as you can,

there are at least 3 different ways to solve this problem.

"""

# Rotate the entire array 'k' times

# T(n)- O(nk)

def rotate_one_by_one(nums, k):

"""

:type nums: List[int]

:type k: int

:rtype: void Do not return anything, modify nums in-place instead.

"""

n = len(nums)

for i in range(k):

temp = nums[n-1]

for j in range(n-1, 0, -1):

nums[j] = nums[j-1]

nums[0] = temp

# Reverse segments of the array, followed by the entire array

# T(n)- O(n)

def rotate(nums, k):

"""

:type nums: List[int]

:type k: int

:rtype: void Do not return anything, modify nums in-place instead.

"""

n = len(nums)

k = k % n

reverse(nums, 0, n - k - 1)

reverse(nums, n - k, n - 1)

reverse(nums, 0, n - 1)

def reverse(array, a, b):

while a < b:

array[a], array[b] = array[b], array[a]

a += 1

b -= 1

algorithms/array/rotate_array.py at master · DaMacho/algorithms · GitHub

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