Inorder Successor in Binary Search Tree-优快云博客

本文介绍了一种在二叉搜索树中寻找指定节点的中序后继节点的方法。提供了两种解决方案：一种利用节点右子树的最小值作为后继；另一种通过递归遍历整棵树找到目标节点的后继。

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

 1 public class Solution {
 2 
 3     public TreeNode inorderSuccessor(TreeNode root, TreeNode n) {
 4         if (root == null) return null;
 5 
 6         if (n.right != null) {
 7             return min(n.right);
 8         }
 9 
10         TreeNode succ = null;
11         while (root != null) {
12             if (n.val < root.val) { //左子树的successor都是当前树的root。
13                 succ = root;
14                 root = root.left;
15             } else if (n.val > root.val)
16                 root = root.right;
17             else
18                 break;
19         }
20         return succ;
21     }
22 
23     public TreeNode min(TreeNode n) {
24         if (n.left != null) {
25             return min(n.left);
26         }
27         return n;
28     }
29 }
30 
31 class TreeNode {
32     TreeNode left;
33     TreeNode right;
34     int val;
35 
36     public TreeNode(int i) {
37         val = i;
38     }
39 }

Another solution

 1 public class Solution {
 2     TreeNode pre = null;
 3     TreeNode succ = null;
 4 
 5     void inorderSuccessorII(TreeNode root, TreeNode p) {
 6         if (root == null || succ != null)
 7             return;
 8         inorderSuccessor(root.left, p);
 9         if (pre == p) {
10             succ = root;
11         }
12         pre = root;
13         inorderSuccessor(root.right, p);
14     }
15 }