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:
分析：采用递归的方法，先判断左子树和右子树是不是BST，如果不是返回false，如果左子树和右子树均为BST，那么再比较左子树最大值、根的值、右子树最小值的关系，如果左子树最大值<根值<右子树最小值，则返回true.代码如下：
1 class Solution { 2 public: 3 bool isValidBST(TreeNode *root) { 4 if(!root) return true; 5 if(isValidBST(root->left)){ 6 int sub_max = tree_max(root->left); 7 if(sub_max >= root->val) return false; 8 }else return false; 9 if(isValidBST(root->right)){ 10 int sub_min = tree_min(root->right); 11 if(sub_min <= root->val) return false; 12 }else return false; 13 return true; 14 } 15 int tree_max(TreeNode * root){ 16 if(!root) return INT_MIN; 17 int tmax = root->val; 18 TreeNode * p = root->right; 19 while(p){ 20 tmax = p->val; 21 p = p->right; 22 } 23 return tmax; 24 } 25 int tree_min(TreeNode * root){ 26 if(!root) return INT_MAX; 27 int tmin = root->val; 28 TreeNode * p = root->left; 29 while(p){ 30 tmin = p->val; 31 p = p->left; 32 } 33 return tmin; 34 } 35 };
Validate Binary Search Tree,布布扣,bubuko.com
标签：des style blog color io strong ar div
原文地址：http://www.cnblogs.com/Kai-Xing/p/3919224.html
