LeetCode 653. Two Sum IV - Input is a BST

Posted zeroingToOne

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了LeetCode 653. Two Sum IV - Input is a BST相关的知识,希望对你有一定的参考价值。

Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target.

Example 1:

Input: 
    5
   /   3   6
 / \   2   4   7

Target = 9

Output: True

 

Example 2:

Input: 
    5
   /   3   6
 / \   2   4   7

Target = 28

Output: False

题意:给定一棵二叉查找树和一个目标值target,判断BST中是否存在两个元素使其相加和为target
思路:用深度优先搜索,将二叉树中的所有节点值放入ArrayList,然后判断是否存在相加为target的两个元素,实现如下:
public boolean findTarget(TreeNode root, int k) {
        List<Integer> nodes = new ArrayList<>();
        dfs(root, nodes);
        for(int i = 0; i < nodes.size(); i++){
            int val = nodes.get(i);
            if(nodes.contains(k - val) && k - val != val)
                return true;
        }
        return false;
    }
    public void dfs(TreeNode root, List<Integer> nodes){
        if(root != null){
            nodes.add(root.val);
            dfs(root.left, nodes);
            dfs(root.right, nodes);
        }
    }

 

 




以上是关于LeetCode 653. Two Sum IV - Input is a BST的主要内容,如果未能解决你的问题,请参考以下文章

LeetCode 653. Two Sum IV - Input is a BST

leetcode 653. Two Sum IV - Input is a BST

[Leetcode]653.Two Sum IV - Input is a BST

[Leetcode] Binary tree--653. Two Sum IV - Input is a BST

653. Two Sum IV - Input is a BST

LeetCode 653. Two Sum IV - Input is a BST(在BST中寻找两个节点,使它们的和为一个给定值)