Solution.py

"""

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.
Return any answer array that satisfies this condition.
 
Example 1:

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.

Example 2:

Input: nums = [2,3]
Output: [2,3]

 
Constraints:

2 <= nums.length <= 2 * 104
nums.length is even.
Half of the integers in nums are even.
0 <= nums[i] <= 1000

 
Follow Up: Could you solve it in-place?

"""


class Solution:
    def sortArrayByParityII(self, nums: List[int]) -> List[int]:
        a, b = 0, 1
        n = len(nums)
        while a < n and b < n:
            if nums[a] % 2 == 0:
                a += 2
            elif nums[b] % 2 == 1:
                b += 2
            else:
                nums[a], nums[b] = nums[b], nums[a]
                a += 2
                b += 2
        return nums