/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool f(TreeNode* root , int k)
    {
        if(root)
        {
            if(!f(root->left , k)) return false;
            if(root->val < k) return false;
            k = root->val;
            if(!f(root->right , k)) return false;
        }

        return true;
    }

    int pathSum(TreeNode* root) {
        if( f(root, -0x3f3f3f3f))
        cout<<"是二叉排序树"<<endl;
        else 
        cout<<"不是二叉排序树"<<endl;
    }
};