LeetCode 700 Search in a Binary Search Tree

给予一棵树:
        4
       / \
      2   7
     / \
    1   3

  2     
 / \   
1   3

/**
 * 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) {
        while (root != null) {
            if (root.val < val) {
                root = root.right;
            } else if (root.val > val) {
                root = root.left;
            } else {
                return root;
            }
        }
        return root;
    }
}