Leetcode: 653. Two Sum IV

超时代码：只多了一个bool变量就超时了

import java.util.ArrayList;
import java.util.List;


public class SumBSt {
    
    public boolean findTarget(TreeNode root, int k) {
        if(root==null) return false;
        List<Integer> list = new ArrayList<>();
        inSort(root,list);
        boolean bool = false;
        int left=0;
        int right=list.size()-1;
        while(left<right){
            if(list.get(left)+list.get(right)==k){
                bool = true;  
            }else if(list.get(left)+list.get(right)<k){
                left++;
            }else{
                right--;
            }
        }
        return bool;
    }
    private void inSort(TreeNode root,List<Integer> list){
        if(root==null) return;
        
        inSort(root.left,list);
        list.add(root.val);
        inSort(root.right,list);
    }
}

accpt的代码，把二叉树前序遍历得到list，顺序是从小到大排列的

import java.util.ArrayList;
import java.util.List;


public class SumBSt {
    
    public boolean findTarget(TreeNode root, int k) {
        if(root==null) return false;
        List<Integer> list = new ArrayList<>();
        inSort(root,list);
        int left=0;
        int right=list.size()-1;
        while(left<right){
            if(list.get(left)+list.get(right)==k){
                return  true;  
            }else if(list.get(left)+list.get(right)<k){
                left++;
            }else{
                right--;
            }
        }
        return false;
    }
    private void inSort(TreeNode root,List<Integer> list){
        if(root==null) return;
        
        inSort(root.left,list);
        list.add(root.val);
        inSort(root.right,list);
    }
}