Validate Binary Search Tree

标签：des   style   blog   color   io   strong   ar   div   

Given a binary tree, determine if it is a valid binary search tree (BST).

Assume a BST is defined as follows:

• The left subtree of a node contains only nodes with keys less than the node‘s key.
• The right subtree of a node contains only nodes with keys greater than the node‘s key.
• Both the left and right subtrees must also be binary search trees.

思路：对输入二叉树进行中序遍历，检查中序遍历序列是否递增。

 1 class Solution {
 2 public:
 3     bool isValidBST( TreeNode *root ) {
 4         prev = 0;
 5         InOrder( root );
 6     }
 7 private:
 8     bool InOrder( TreeNode *node ) {
 9         if( !node ) { return true; }
10         if( !InOrder( node->left ) ) { return false; }
11         if( prev && prev->val >= node->val ) { return false; }
12         prev = node;
13         return InOrder( node->right );
14     }
15     TreeNode *prev;
16 };

Validate Binary Search Tree,布布扣,bubuko.com

Validate Binary Search Tree

标签：des   style   blog   color   io   strong   ar   div   

原文地址：http://www.cnblogs.com/moderate-fish/p/3918253.html