// test.cpp : Defines the entry point for the console application.//#include "stdafx.h"#include <iostream>using namespace std;typedef struct BTree{    char val;    struct BTree *lchild,*rchild;}BTree;//先序建立二叉树BTree * CreateBTree(BTree *T)  {      char value;     cin >> value;      if(‘#‘ == value)          T = NULL;      else      {          T = new BTree;          T->val = value;          cout<<"left of "<<T->val<<" :"<<endl;        T->lchild=CreateBTree(T->lchild);          cout<<"right of "<<T->val<<" :"<<endl;        T->rchild=CreateBTree(T->rchild);      }    return T;}   
/*建立二叉排序树*/BTree* insertNode(BTree *Root,int value){        BTree* p=new BTree();    p->val=value;    p->lchild=NULL;    p->rchild=NULL;    if(Root==NULL)    {        Root=p;        return Root;    }    if(value<=Root->val)        Root->lchild=insertNode(Root->lchild,value);    else if(value>Root->val)        Root->rchild=insertNode(Root->rchild,value);    return Root;    }//先序遍历二叉树void PreOrderTraverse(BTree* T){    if(T){        printf("%c ",T->val);        PreOrderTraverse(T->lchild);        PreOrderTraverse(T->rchild);    }}//中序遍历void InOrderTraverse(BTree* T){    if(T){        InOrderTraverse(T->lchild);        printf("%c ",T->val);        InOrderTraverse(T->rchild);    }}//后序遍历void PostOrderTraverse(BTree* T){    if(T){        PostOrderTraverse(T->lchild);        PostOrderTraverse(T->rchild);        printf("%c ",T->val);    }}
//递归遍历二叉树是否为二叉排序树int IsSearchTree(BTree *t)  {    if(!t)        //空二叉树情况        return 1;    else if(!(t->lchild) && !(t->rchild))   //左右子树都无情况        return 1;    else if((t->lchild) && !(t->rchild))    //只有左子树情况    {        if(t->lchild->val>t->val)            return 0;        else            return IsSearchTree(t->lchild);    }    else if((t->rchild) && !(t->lchild))   //只有右子树情况    {        if(t->rchild->val<t->val)            return 0;        else            return IsSearchTree(t->rchild);    }    else         //左右子树全有情况    {        if((t->lchild->val>t->val) || (t->rchild->val<t->val))            return 0;        else            return ( IsSearchTree(t->lchild) && IsSearchTree(t->rchild) );    }}/*写法复杂，但代码少的判断二叉排序树的方法*/int Prev=INT_MIN;int JudgeBST(BTree *t){    int b1,b2;    if (t==NULL)        return 1;    else{        b1=JudgeBST(t->lchild);        if (b1==0||Prev>=t->val)            return 0;        Prev=t->val;        b2=JudgeBST(t->rchild);        return b2;    }}int main(int argc, char* argv[]){    /*建立*/    BTree *root=new BTree();    printf("creating a binary tree with root:\n");    root=CreateBTree(root);    /*输出*/    PreOrderTraverse(root);    printf("\n");    InOrderTraverse(root);    printf("\n");    PostOrderTraverse(root);    printf("\n");    /*是否排序树*/    printf("%d\n",IsSearchTree(root));    printf("%d\n",JudgeBST(root));    system("pause");    return 0;}