双指针法

class Solution {
    public int[] sortedSquares(int[] nums) {
      int i = 0,j = nums.length - 1;
      int []res = new int[nums.length];
      int k = nums.length -1;
      while(i<=j){
        if(nums[i]*nums[i]<nums[j]*nums[j]){
            res[k] = nums[j] *nums[j];
            j--;
        } 
        else{
            res[k] = nums[i] *nums[i];
            i++;
        } 
        k--;
      }
      return res;
    }
}