# [LeetCode] Inorder Successor in BST

Inorder Successor in BST

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.

1 /**
2  * Definition for a binary tree node.
3  * struct TreeNode {
4  *     int val;
5  *     TreeNode *left;
6  *     TreeNode *right;
7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
8  * };
9  */
10 class Solution {
11 public:
12     TreeNode* inorderSuccessor(TreeNode* root, TreeNode* p) {
13         if (p == NULL) return NULL;
14         TreeNode *res = NULL;
15         if (p->right != NULL) {
16             res = p->right;
17             while (res->left) res = res->left;
18             return res;
19         }
20         TreeNode *q = root;
21         while (q != NULL && q->val != p->val) {
22             if (q->val > p->val) {
23                 res = q;
24                 q = q->left;
25             } else {
26                 q = q->right;
27             }
28         }
29         return res;
30     }
31 };

posted @ 2015-09-22 14:47  Eason Liu  阅读(672)  评论(0编辑  收藏  举报