|
| 1 | +/* |
| 2 | + * @lc app=leetcode id=653 lang=java |
| 3 | + * |
| 4 | + * [653] Two Sum IV - Input is a BST |
| 5 | + */ |
| 6 | + |
| 7 | +// @lc code=start |
| 8 | +/** |
| 9 | + * Definition for a binary tree node. |
| 10 | + * public class TreeNode { |
| 11 | + * int val; |
| 12 | + * TreeNode left; |
| 13 | + * TreeNode right; |
| 14 | + * TreeNode() {} |
| 15 | + * TreeNode(int val) { this.val = val; } |
| 16 | + * TreeNode(int val, TreeNode left, TreeNode right) { |
| 17 | + * this.val = val; |
| 18 | + * this.left = left; |
| 19 | + * this.right = right; |
| 20 | + * } |
| 21 | + * } |
| 22 | + */ |
| 23 | +class Solution { |
| 24 | + public boolean findTarget(TreeNode root, int k) { |
| 25 | + if (root == null) return false; |
| 26 | + Set<Integer> set = new HashSet<>(); |
| 27 | + return dfs(root, set, k); |
| 28 | + } |
| 29 | + |
| 30 | + private boolean dfs(TreeNode root, Set<Integer> set, int k) { |
| 31 | + if (root == null) return false; |
| 32 | + if (set.contains(k - root.val)) { |
| 33 | + return true; |
| 34 | + } |
| 35 | + set.add(root.val); |
| 36 | + return dfs(root.left, set, k) || dfs(root.right, set, k); |
| 37 | + } |
| 38 | +} |
| 39 | +// @lc code=end |
| 40 | + |
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