977. Squares of a Sorted Array

Problem Link

Description

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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

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Python3

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

Python

class Solution(object):
    def sortedSquares(self, A):
        """
        :type A: List[int]
        :rtype: List[int]
        """
        lst = []
        for i in A:
            lst.append(i**2)
        
        lst.sort()
        return lst