4. Squares of a Sorted Array (#977) [EASY]

Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order.

Example 1:

Input: [-4,-1,0,3,10]
Output: [0,1,9,16,100]

Example 2:

Input: [-7,-3,2,3,11]
Output: [4,9,9,49,121]

Note:

1. 1 <= A.length <= 10000
2. -10000 <= A[i] <= 10000
3. A is sorted in non-decreasing order.

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

My solution: O(nlogn)

class Solution:
    def sortedSquares(self, A: List[int]) -> List[int]:
        return sorted([value**2 for value in A])

Note: sorted() in Python is O(nlogn)

O(n)

class Solution:
    def sortedSquares(self, lst: List[int]) -> List[int]:
        negative = [e ** 2 for e in lst if e < 0][::-1] 
        positive = [e ** 2 for e in lst if e >= 0]
        res = []
        i, j = 0, 0
        while i < len(negative) and j < len(positive):
            if negative[i] < positive[j]:
                res.append(negative[i])
                i += 1
            else:
                res.append(positive[j])
                j += 1
while i < len(negative):
            res.append(negative[i])
            i += 1
while j < len(positive):
            res.append(positive[j])
            j += 1
return res