Double pointer | 977 Square of ordered array

One 、 subject

Two 、 Answer key

Double pointer
Left pointer ： Traverse from left to right , Divide valid value boundary , At this time, the array of valid values is [0,left]
Right pointer ： Traverse from right to left , Divide valid value boundary , At this time, the array of valid values is [right,nums.size()-1]

3、 ... and 、 Code

class Solution {
    
public:
    vector<int> sortedSquares(vector<int>& nums) {
    
    int right = nums.size() - 1;
    int left = 0;
    vector<int> ans(nums.size());
    int pos =nums.size() - 1;
    while(left < right){
    
        if(nums[left] * nums[left] > nums[right] * nums[right]){
    
            ans[pos--] = nums[left] * nums[left];
            left++;
        }else{
    
            ans[pos--] = nums[right] * nums[right];
            right--;
        } 
    }
    ans[pos] = nums[left] * nums[left];
    return ans;
    }
};