以下代码运行后只有A一个字符，估计是create函数出错，请高手解释，谢谢~~！
#include<stdio.h>
#include<malloc.h>
#define MAXSIZE 100
typedef struct node
{
    char data;
    struct node *lchild;
    struct node *rchild;
}btnode;
btnode *creatbtnode(btnode *b,char *str)
{
    btnode *st[MAXSIZE],*p=NULL;
    int top=-1,k,j=0;
    char ch;
    b=NULL;
    ch=str[j];
    while(ch!='\0')
    {
        switch(ch)
        {
        case '(': top++;st[top]=p;k=1;break;
        case ')': top--;break;
        case ',': k=2;break;
        default : p=(btnode *)malloc(sizeof(btnode));
            p->data=ch;
            p->lchild=NULL;
            p->rchild=NULL;
            if(b==NULL)
                b=p;
            else
            {
                switch(k)
                {
                case '1' : st[top]->lchild=p;break;
                case '2' : st[top]->rchild=p;break;
                }
            }
        }
        j++;
        ch=str[j];
    }
    return b;
}
btnode *findnode(btnode *b,char x)/*返回值域x的结点的指针*/
{
    btnode *p;
    if(b==NULL)
        return NULL;
    else if(b->data==x)
        return b;
    else
    {
        p=findnode(b->lchild,x);
        if(p!=NULL)
            return p;
        else
            return(findnode(b->rchild,x));
    }
}
btnode *lchildnode(btnode *p)
{
    return p->lchild;
}
btnode *rchildnode(btnode *p)
{
    return p->rchild;
}
int btnodedepth(btnode *b)/*求树高*/
{
    int lchilddep,rchilddep;
    if(b==NULL)
        return 0;
    else
    {
        lchilddep=btnodedepth(b->lchild);
        rchilddep=btnodedepth(b->rchild);
        return((lchilddep>rchilddep)?(lchilddep+1):(rchilddep+1));
    }
}
void disbtnode(btnode *b)
{
    if(b!=NULL)
    {
        printf("%c",b->data);
        if(b->lchild!=NULL||b->rchild!=NULL)
        {
            printf("(");
            disbtnode(b->lchild);
            if(b->rchild!=NULL)
                printf(",");
            disbtnode(b->rchild);
            printf(")");
        }
    }
}
int btnodewidth(btnode *b)
{
    struct
    {
        int lno;/*结点层次编号*/
        btnode *p;
    }qu[MAXSIZE];
    int front=0,rear=0;
    int lnum,max,i,n;
    if(b!=NULL)
    {
        rear++;
        qu[rear].p=b;
        qu[rear].lno=1;
        while(rear!=front)
        {
            front++;
            b=qu[front].p;
            lnum=qu[front].lno;
            if(b->lchild!=NULL)
            {
                rear++;
                qu[rear].p=b->lchild;
                qu[rear].lno=lnum+1;
            }
            if(b->rchild!=NULL)
            {
                rear++;
                qu[rear].p=b->rchild;
                qu[rear].lno=lnum+1;
            }
        }
        max=0;
        lnum=1;
        i=1;
        while(i<=rear)
        {
            n=0;
            while(i<=rear&&qu[i].lno==lnum)
            {
                n++;
                i++;
            }
            lnum=qu[i].lno;
            if(n>max)max=n;
        }
        return max;
    }
    else
        return 0;
}
int node(btnode *b)
{
    int num1,num2;
    if(b==NULL)
        return 0;
    else if(b->lchild==NULL&&b->rchild==NULL)
        return 1;
    else 
    {
        num1=node(b->lchild);
        num2=node(b->rchild);
        return(num1+num2+1);
    }
}
int leafnodes(btnode *b)
{
    int num1,num2;
    if(b==NULL)
        return 0;
    else if(b->lchild==NULL&&b->rchild==NULL)
        return 1;
    else
    {
        num1=leafnodes(b->lchild);
        num2=leafnodes(b->rchild);
        return(num1+num2);
    }
}
void main()
{
    btnode *b,*p,*lp,*rp;
    b=creatbtnode(b,"A(B(D,E(H(J,K(L,M(,N))))),C(F,G(,I)))");
    printf("(1)output tree:   ");
    disbtnode(b);
    printf("\n");
    printf("(2)H point: ");
    p=findnode(b,'H');
    if(p!=NULL)
    {
        lp=lchildnode(p);
        if(lp!=NULL)
            printf("left child is :%c  ",lp->data);
        else
            printf("no child  ");
        rp=rchildnode(p);
            if(rp!=NULL)
                printf("right child is :%c  ",rp->data);
            else
                printf("no child  ");
    }
    printf("\n");
    printf("(3)the depth :%d\n",btnodedepth(b));
    printf("(4)the width :%d\n",btnodewidth(b));
    printf("(5)the point :%d\n",node(b));
    printf("(6)the leafpoint :%d\n",leafnodes(b));