#include 
     
      #define maxSize 5using namespace std;typedef struct BTNode{    char data;    struct BTNode * lchild;    struct BTNode * rchild;}BTNode;BTNode * initBTNode(){    BTNode *node = (BTNode*)malloc(sizeof(BTNode));    node->lchild=0;    node->rchild=0;    return node;}BTNode * init(BTNode *p){    BTNode *A=initBTNode();    BTNode *B=initBTNode();    BTNode *C=initBTNode();    BTNode *D=initBTNode();    BTNode *E=initBTNode();    BTNode *F=initBTNode();            A->data='A';    B->data='B';    C->data='C';    D->data='D';    E->data='E';    F->data='F';        C->lchild=E;    C->rchild=F;    B->lchild=D;    A->rchild=C;    A->lchild=B;    p=A;    return p;}void visit(BTNode *p){    cout << p->data << " ";}void preorder(BTNode *p){    if(p!=0)    {        visit(p);        preorder(p->lchild);        preorder(p->rchild);    }}void inorder(BTNode *p){    if(p!=0)    {        inorder(p->lchild);        visit(p);        inorder(p->rchild);    }}void postorder(BTNode *p){    if(p!=0)    {        postorder(p->lchild);        postorder(p->rchild);        visit(p);    }}void level(BTNode *p){    int front,rear;    BTNode *que[maxSize];    front = rear = 0;    BTNode *q;    if(p!=0)    {        rear=(rear+1)%maxSize;        que[rear]=p;        while(front!=rear)        {            front = (front+1)%maxSize;            q=que[front];            visit(q);            if(q->lchild!=0)            {                rear=(rear+1)%maxSize;                que[rear]=q->lchild;            }            if(q->rchild!=0)            {                rear=(rear+1)%maxSize;                que[rear]=q->rchild;            }        }    }}int main(int argc, char* argv[]){    BTNode *node=new BTNode;    BTNode *p=init(node);    cout << "先序遍历：" ;    preorder(p);    cout << endl;    cout << "中序遍历：" ;    inorder(p);    cout << endl;    cout << "后序遍历：" ;    postorder(p);    cout << endl;    cout << "层次遍历：" ;    level(p);    cout << endl;    return 0;}