Sort Array by Parity – Java

This solution runs in 0(n) time (linear) and uses O(1) space (constant) and is based on the Dutch National Flag Problem.

class Solution {
    public int[] sortArrayByParity(int[] A) {
        int low = 0, mid = 0, high = A.length - 1;
        int temp;
        while (mid <= high) {
            if (A[mid] == 0) {
                temp = A[mid];
                A[mid] = A[low];
                A[low] = temp;
                low++;
                mid++;
            } else if (A[mid] % 2 == 0) {
                mid++;
            } else {
                temp = A[mid];
                A[mid] = A[high];
                A[high] = temp;
                high--;
            }
        }
        return A;
    }
}