0062_P977_Squares_of_a_Sorted_Array.cpp

/* 
Day: 62
Problem Number: 977 (https://leetcode.com/problems/squares-of-a-sorted-array)
Date: 02-03-2024 
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 <= 10^4
* -10^4 <= nums[i] <= 10^4
* 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?

Code:  */
class Solution {
public:
    vector<int> sortedSquares(vector<int>& nums) {
        int n = nums.size();
        vector<int> res(n);
        for (int i = 0, j = n - 1, k = n - 1; i <= j;) {
            if (nums[i] * nums[i] > nums[j] * nums[j]) {
                res[k--] = nums[i] * nums[i];
                ++i;
            } else {
                res[k--] = nums[j] * nums[j];
                --j;
            }
        }
        return res;
    }
};