977

977. Squares of a Sorted Array (Easy)

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?

Related Topics:
Array, Two Pointers

Similar Questions:

• Merge Sorted Array (Easy)
• Sort Transformed Array (Medium)

Solution 1.

// OJ: https://leetcode.com/problems/squares-of-a-sorted-array/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    vector<int> sortedSquares(vector<int>& A) {
        int N = A.size();
        for (int &n : A) n *= n;
        vector<int> ans(N);
        for (int i = 0, j = N - 1, k = N - 1; i <= j; ) {
            if (A[i] > A[j] ) {
                ans[k--] = A[i];
                ++i;
            } else {
                ans[k--] = A[j];
                --j;
            }
        }
        return ans;
    }
};