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977. Squares of a Sorted Array

Difficulty Topics

Description

Given an integer array nums sorted in non-decreasing order, return an array of the squares of each number sorted in non-decreasing order.

 

Example 1:

Input: nums = [-4,-1,0,3,10]
Output: [0,1,9,16,100]
Explanation: After squaring, the array becomes [16,1,0,9,100].
After sorting, it becomes [0,1,9,16,100].

Example 2:

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

 

Constraints:

  • 1 <= nums.length <= 104
  • -104 <= nums[i] <= 104
  • nums is sorted in non-decreasing order.

 

Follow up: Squaring each element and sorting the new array is very trivial, could you find an O(n) solution using a different approach?

Solution

squares-of-a-sorted-array.py
class Solution:
    def sortedSquares(self, nums: List[int]) -> List[int]:
        n = len(nums)
        res = [0] * n
        i, j, p = 0, n - 1, n - 1

        while i <= j:
            if abs(nums[i]) >= abs(nums[j]):
                res[p] = nums[i] * nums[i]
                i += 1
            else:
                res[p] = nums[j] * nums[j]
                j -= 1

            p -= 1

        return res