動機

原來已經sort過了!!

Problem

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?

Sol

這裡的重點是要從平方後最大的開始塞!!

class Solution:
    def sortedSquares(self, nums: List[int]) -> List[int]:
        ret = []
        i,j = 0,len(nums)-1
        while i <= j:
            if abs(nums[i]) < abs(nums[j]):
                n = nums[j]
                j -= 1
            else:
                n = nums[i]
                i += 1
            ret.append(n*n)
        ret.reverse()
        return ret