判别是否二叉排序树（耿8.6）

 

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
using namespace std;

typedef struct node{
	int info;
	node* lchild;
	node* rchild;
}node,*Pnode;




Pnode creatnode(){
	int c;
	Pnode p;
	
	cin>>c;

	if(c==-1)   p=NULL;	
	else{
		p=(Pnode)malloc(sizeof(node));
		p->info=c;
		p->lchild=creatnode();
		p->rchild=creatnode();
	}
	return p;
} //先序创建二叉树 


int isBSTree(Pnode t){
	if(t->lchild==NULL&&t->rchild==NULL) return 1;
	else if(t->lchild==NULL) {
		if(t->rchild->info>t->info) {
		return	isBSTree(t->lchild);
		}
		else return 0;
	}
	else if(t->rchild==NULL) {
		if(t->lchild->info<t->info) {
		return	isBSTree(t->lchild);
		}
		else return 0;
	}
	else{
		if(t->lchild->info<t->info&&t->rchild->info>t->info) {
			return (isBSTree(t->lchild)&&isBSTree(t->rchild));
		}
		else return 0; 
	}
	 
}

void printnode(Pnode t){
	if(t) {
	cout<<t->info;
	printnode(t->lchild);
	printnode(t->rchild);
	}
	
}
int main(){	
Pnode gen=(Pnode)malloc(sizeof(node));
	gen=creatnode();
//	cout<<"lalalal"<<endl;
int flag=isBSTree(gen);
if(flag==1) cout<<"yes"<<endl;
else cout<<"no"<<endl;

	
}