leetcode 653 Two Sum IV - Input is a BST

문제

숫자가 담긴 바이너리서치트리와 타겟번호가 주어졌을때 더했을때 합이 타겟과 일치하는지 boolean으로 리턴시켜라

 

https://leetcode.com/problems/two-sum-iv-input-is-a-bst/

Two Sum IV - Input is a BST - LeetCode

예제 bst는 링크참조

 

 

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean findTarget(TreeNode root, int k) {
       HashSet<Integer> hashs = new HashSet<Integer>();
       return dfs(root,hashs,k);
    }
    
    public boolean dfs (TreeNode root,HashSet<Integer> hash, int k) {
        
        if (root == null) {
            return false;
        }
        
        if (hash.contains (k - root.val)) {
            return true;
        }
        
        hash.add(root.val);
        
        return dfs(root.left,hash,k) || dfs(root.right,hash,k);        
    }
}