Squares of a Sorted Array

 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?

class Solution {

public:

    vector<int> sortedSquares(vector<int>& nums) {

        vector<int> ans(nums.size(), 0);

        int end = nums.size() - 1;

        int st = 0;

        int iter = nums.size() - 1;

        while (st <= end) {

            if (abs(nums[end]) > abs(nums[st])) {

                ans[iter] = nums[end] * nums[end];

                end--;

            } else {

                ans[iter] = nums[st] * nums[st];

                st++;

            }

            iter--;

        }

        return ans;

    }

};