leetcode_num98_Validate Binary Search Tree

判断是否为二叉搜索树

定义上下确界

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool isValidBST(TreeNode *root) {        return isValidBSTRe(root,LONG_MIN,LONG_MAX);//LONG_MIN,LONG_MAX set the bound    }    bool isValidBSTRe(TreeNode *root,long min,long max){//parameter type long        if(!root)            return true;        else if(root->val<=min||root->val>=max)            return false;        else            return isValidBSTRe(root->left,min,root->val)&&isValidBSTRe(root->right,root->val,max);    }};