977. Squares of a Sorted Array

Posted on Edited on In

977. Squares of a Sorted Array

Description

Difficulty: Easy

Related Topics: Array, Two Pointers, Sorting

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:

1
2
3
4
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:

1
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?

Hints/Notes

Solution

Language: C++

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
class Solution {
public:
    vector<int> sortedSquares(vector<int>& nums) {
        int i = 0, j = nums.size() - 1, idx = nums.size() - 1;
        vector<int> res(nums.size(), 0);
        while (i <= j) {
            if (abs(nums[i]) < abs(nums[j])) {
                res[idx--] = nums[j] * nums[j];
                j--;
            } else {
                res[idx--] = nums[i] * nums[i];
                i++;
            }
        }
        return res;
    }
};