判断二叉树是否为二叉排序树

#include 
#include 
#include 
#include
using namespace std;

#define MINKEY INT_MIN             //关键字的下限

class Treenode{
public:
    int data;
    Treenode * lchild;
    Treenode * rchild;
};
typedef struct Treenode* Bitree;

void CreatBitree(Bitree &T,int a[],int &i){
    i++;
    if(a[i]==0) {T=NULL;return;}
    T=new Treenode;
    T->data=a[i];
    CreatBitree(T->lchild,a,i);
    CreatBitree(T->rchild,a,i);

}
void CreatBitree(Bitree &T,int a[]){
    int i=-1;
    CreatBitree(T,a,i);
}

void IsBstree(Treenode *T,int &pre,bool &flag){
    if(flag==true){
        if(T->lchild){
            IsBstree(T->lchild,pre,flag);
        }
        if(T->data>=pre){
            pre=T->data;
        }
        else flag=false;
        if(T->rchild){
            IsBstree(T->rchild,pre,flag);
        }
    }
}

bool IsBstree(Treenode *T){
    int pre=MINKEY;
    bool flag=true;
    IsBstree(T,pre,flag);
    return flag;
}

/*bool IsBstree( Treenode *T){
    if(T==NULL) return true;                            //树为空
    else if(!T->lchild&&!T->rchild) return true;        //左右子树为空
    else if(T->lchild&&!T->rchild){                     //左不空右空
        if(T->lchild->data>T->data){
            return false;
        }
        else return IsBstree(T->lchild);
    }
    else if(!T->lchild&&T->rchild){                       //右空左不空
        if(T->rchild->datadata){
            return false;
        }
        else return IsBstree(T->rchild);
    }
    else {                                           //左右都不空
        if((T->lchild->data>T->data)||(T->rchild->datadata)){
            return false;
        }
        else return (IsBstree(T->lchild)&&IsBstree(T->rchild));
    }

}*/
int main (){
    Bitree A;
    int a[20]={10,7,3,0,0,8,0,0,12,11,0,0,15,0,0,0};
    CreatBitree(A,a);
    if(IsBstree(A))  cout<<"二叉树A是二叉排序树"<