LeetCode Inorder Successor in BST

原题链接在这里：https://leetcode.com/problems/inorder-successor-in-bst/

题目：

Given a binary search tree and a node in it, find the in-order successor of that node in the BST.

Note: If the given node has no in-order successor in the tree, return null.

题解：

successor could be自己的parent, or 右子树中最左的点.

For both cases, if p.val < root.val, update successor as root. Otherwise, root needs to be bigger, root = root.right.

Time Complexity: O(h).

Space: O(1).

AC Java:

 /**
  * Definition for a binary tree node.
  * public class TreeNode {
  *     int val;
  *     TreeNode left;
  *     TreeNode right;
  *     TreeNode(int x) { val = x; }
  * }
  */
 public class Solution {
     public TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
         if(root == null || p == null){
             return null;
         }
         TreeNode successor = null;
         while(root != null){
             if(p.val < root.val){
                 successor = root;
                 root = root.left;
             }else{
                 root = root.right;
             }
         }
         return successor;
     }
 }

跟上Inorder Successor in BST II.