Sort Array By Parity II — LeetCode 922 Python Solution

The problem

Given an array of integers nums, half of the integers in nums are odd, and the other half are even. Sort the array so that whenever nums[i] is odd, i is odd, and whenever nums[i] is even, i is even.

Example

Input

nums = [4,2,5,7]

Output

[4,5,2,7]

Explanation

[4,7,2,5], [2,5,4,7], [2,7,4,5] would also have been accepted.

Python solution

class Solution:
    def sortArrayByParityII(self, nums: List[int]) -> List[int]:
        n, j = len(nums), 1
        for i in range(0, n, 2):
            if nums[i] % 2:
                while nums[j] % 2:
                    j += 2
                nums[i], nums[j] = nums[j], nums[i]
        return nums

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 922. Sort Array By Parity II 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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