[算法]如何判断一棵二叉树是二叉搜索树

方法一: 中序遍历

#include <stdio.h>

typedef struct _node{
    struct _node *left, *right;
    int data;
}node;

int helper(node *left, node *root, node *right){
    if(root == NULL)
        return 1;
    
    if(left != NULL  && helper(left->left, left, left->right)==0)
        return 0;
    
    if(right != NULL && helper(right->left, right, right->right)==0)
        return 0;

    if(left->data>root->data || root->data<right->data)
        return 0;
}

方法二: 取出左右子树最值,与根节点比较