LeetCode-Search in a Binary Search Tree

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Description：
Given the root node of a binary search tree (BST) and a value. You need to find the node in the BST that the node’s value equals the given value. Return the subtree rooted with that node. If such node doesn’t exist, you should return NULL.

For example,

Given the tree:
        4
       / \
      2   7
     / \
    1   3

And the value to search: 2

You should return this subtree:

      2     
     / \   
    1   3

In the example above, if we want to search the value 5, since there is no node with value 5, we should return NULL.

Note that an empty tree is represented by NULL, therefore you would see the expected output (serialized tree format) as [], not null.

题意：给定一颗BST树（二叉搜索树）和一个要查找的值，返回这个值再树中对应树的根节点；

解法：对于一颗BST树来说，其根节点大于左节点且小于右节点；因此，我们需要根据这个规则进行比较要查找的值即可；

Java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode searchBST(TreeNode root, int val) {
        if (root == null) {
            return null;
        }   
        if (root.val == val) {
            return root;
        } else if (root.val > val) {
            return searchBST(root.left, val);
        } 
        return searchBST(root.right, val);
    }
}

所有的代码已整理放在GitHub上；