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
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { Map<Integer,Integer> map = new HashMap<>(); int key = 0; public boolean findTarget(TreeNode root, int k) { // Queue<TreeNode> queue = new ArrayDeque<>(); // queue.offer(root); // while(!queue.isEmpty()){ // root = // if() // } find(root); for (Integer value : map.values()) { if(value*2!=k&&map.containsValue(k - value.intValue())) return true; } return false; } void find(TreeNode rr){ if(rr != null){ find(rr.left); map.put(new Integer(key++), new Integer(rr.val)); find(rr.right); } } }
原文：http://www.cnblogs.com/baichangfu/p/7487926.html