Likou 977-Squaring of ordered arrays - brute force method & double pointer method

Title description

Given you an array nums of integers sorted in non-decreasing order, returns a new array of squares of each number, requiring alsoSort by non-decreasing order.

Solution ideas

violence laws

1. traverse the array nums and save the square of each element in the newly created array variable arr;

2. sort arr in ascending order;

3. return arr.

Double pointer method

1. Create two pointer variables first last, pointing to the head and tail of nums respectively;
2. Compare the square values ​​of the elements pointed to by two variables each time, and store the larger one in the high position of arr.

Input and output example

Code

violence laws

class Solution {public int[] sortedSquares(int[] nums) {int len ​​= nums.length;int[] arr = new int[len];for(int i = 0; i < len; i++){arr[i] = nums[i] * nums[i];}Arrays.sort(arr);return arr;}}

Double pointer method

class Solution {public int[] sortedSquares(int[] nums) {int len ​​= nums.length;int[] arr = new int[len];int first = 0, last = len-1;for(int i = len-1; i >= 0; i--){if(nums[first]*nums[first] >= nums[last]*nums[last]){arr[i] = nums[first]*nums[first];first++;}else{arr[i] = nums[last]*nums[last];last--;}}return arr;}}