How to implement square of ordered array in PHP

Given an array A of integers sorted in non-decreasing order, return a new array consisting of the square of each number, which is also required to be sorted in non-decreasing order. Today, the editor will introduce the method of realizing the square of ordered array in PHP. You can refer to it if you need it.

Given an array A of integers sorted in non-decreasing order, return a new array consisting of the square of each number, also sorted in non-decreasing order.

Example 1:

输入：[-4,-1,0,3,10]
输出：[0,1,9,16,100]

Example 2:

输入：[-7,-3,2,3,11]
输出：[4,9,9,49,121]

Solution idea 1

Built-in function solution

Code

class Solution {
    /** 
    * @param Integer[] $A 
    * @return Integer[] 
    */
    function sortedSquares($A) {
        foreach ($A as &$item) {
            $item = $item * $item;
        }
        sort($A);
        return $A;
    }}

Solution idea 2

Double pointer traversal, and with the help of the new array, after calculating the square The results are placed in the new array from large to small.

class Solution {
    /** 
    * 
    *
    * 2 为自乘 2 次，也是平方 
    * @param Integer[] $A 
    * @return Integer[] 
    */
    function sortedSquares($A) {
        $ans = [];
        $i = 0;
        $j = count($A) - 1;
        $k = count($A) - 1;
        while ($i <= $j) {
            // 原数组是有序的，所以 -$A[$i] > $A[$j] 即为 $A[$i] 的绝对值平方后更大 
            if (-$A[$i] > $A[$j]) {
                $ans[$k--] = $A[$i] ** 2;
                // 左指针向右移动
                
                $i++;
            } else {
                $ans[$k--] = $A[$j] ** 2;
                $j--;
            }
        }
        return $ans;
    }}

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