LC189 Rotate Array

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
# solution 1: create extra space and copy
# time O(N) space O(N)
        if not nums or k<=0:
            return 
        copy = []
        size = len(nums)
        for i in range(size):
            copy.append(nums[i])
        for j in range(size):
            nums[(j+k)%size] = copy[j]

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
    # main idea: get the last k , get the first size-k items, and concat them together
    # time O(N) space O(1)
        """
        3 swaps
        """
        # naive solution
        size = len(nums) 
        k = k% size
        def swap(l,r):
            while l<r:
                nums[l],nums[r] = nums[r], nums[l]
                l+= 1
                r -= 1
        swap(0,size-1)
        swap(0,k-1)
        swap(k,size-1)

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        cnt = 0
        start = 0
        cur = 0 
        num_target = nums[0]
        tmp = 0
        size = len(nums)
        # main idea: keep rotating until having rotated n different elements
        while cnt < size:
            num_tar,nums[(cur+k) % size] = nums[(cur+k) % size], num_tar
            cur = (cur+k) % size
            cnt += 1
            if (cur == start):
                break