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rotate_array.py
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rotate_array.py
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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