LC977. Squares of a Sorted Array

class Solution:
    def sortedSquares(self, A: List[int]) -> List[int]:
        """ tc O(N)  sc O(N)
        main idea: two ptr, since A is sorted, we can compare from two end, create a result arr to keep appending relative bigger squared value into res
        note while loop termination condition: l <= r 
        """
        n = len(A)
        res = [0] * n
        l,r,p = 0,n-1,n-1
        while l <= r :
            if abs(A[l]) > abs(A[r]):
                res[p] = A[l]*A[l]
                l += 1
            else:
                res[p] = A[r]*A[r]
                r -= 1 
            p -= 1
        return res