Sort Array By Parity — LeetCode 905 Python Solution

The problem

Given an integer array nums, move all the even integers at the beginning of the array followed by all the odd integers. Return any array that satisfies this condition.

Example

Input

nums = [3,1,2,4]

Output

[2,4,3,1]

Explanation

The outputs [4,2,3,1], [2,4,1,3], and [4,2,1,3] would also be accepted.

Python solution

class Solution:
    def sortArrayByParity(self, nums: List[int]) -> List[int]:
        i, j = 0, len(nums) - 1
        while i < j:
            if nums[i] % 2 == 0:
                i += 1
            elif nums[j] % 2 == 1:
                j -= 1
            else:
                nums[i], nums[j] = nums[j], nums[i]
                i, j = i + 1, j - 1
        return nums

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 905. Sort Array By Parity is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Two Pointers.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

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