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905. Sort Array By Parity

Python​

Two Pointer - Slow and Fast​

class Solution:
    def sortArrayByParity(self, nums: List[int]) -> List[int]:
        if len(nums) < 2:
            return nums

        cur, r = 0, 0

        while r < len(nums):
            if nums[cur] % 2 == 0:
                cur += 1
                r = cur
                continue

            if nums[r] % 2 != 0:
                r += 1
                continue

            nums[cur], nums[r] = nums[r], nums[cur]
            cur += 1

        return nums

Two Pointer - Left Right Approaching​

class Solution:
    def sortArrayByParity(self, nums: List[int]) -> List[int]:
        if len(nums) < 2:
            return nums

        left, right = 0, len(nums)-1

        while left < right:
            if nums[left] % 2 == 0:
                left += 1
            elif nums[right] % 2 != 0:
                right -= 1
            else:
                nums[left], nums[right] = nums[right], nums[left]
                left += 1
                right -= 1

        return nums