二叉树建立，遍历和二叉排序树的判断【c++】

// 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;
}