977. Squares of a Sorted Array

// LeetCode URL: https://leetcode.com/problems/squares-of-a-sorted-array/

/**
 * Two Pointer
 *
 * Refer:
 * https://leetcode.com/problems/squares-of-a-sorted-array/discuss/221922/Java-two-pointers-O(N)
 *
 * Time Complexity: O(N)
 *
 * Space Complexity: O(1) (Excluding the result)
 *
 * N = Length of the input array.
 */
class Solution {
    public int[] sortedSquares(int[] A) {
        if (A == null || A.length == 0) {
            return new int[0];
        }

        int len = A.length;
        int left = 0;
        int right = len - 1;
        int[] result = new int[len];
        int i = len - 1;

        while (left <= right) {
            if (Math.abs(A[right]) >= Math.abs(A[left])) {
                result[i] = A[right] * A[right];
                right--;
            } else {
                result[i] = A[left] * A[left];
                left++;
            }
            i--;
        }

        return result;
    }
}