请各位看一下关于二叉树的程序出了什么错误？

#include <stdio.h>
#include <malloc.h>
#define MAXSIZE 20
typedef struct btnode
{
   char cdata;
   struct btnode *lchild,*rchild;
}BTNode;
BTNode *Create_BiTree()/*二叉树的建立*/
{                /*用辅助数组建立二叉树*/
   int i,j;
   char ch;
   BTNode *s,*t,*p[MAXSIZE];
   printf("输入顶点编号及信息，输入0和#结束:i,ch");
   scanf("%d,%c",&i,&ch);
   while(i!=0 &&ch!='#')/*建立二叉树的存储结构*/
      {s=(BTNode *)malloc(sizeof(BTNode));
       s->cdata=ch;
       s->lchild=s->rchild=NULL;
       p[i]=s;
       if(i==1) t=s;/*判断输入结点是根结点、左孩子还是右孩子*/
       else
         {j=i/2;
          if(i%2==0) p[j]->lchild=s;
          else p[j]->rchild=s;
         }
       printf("输入顶点编号及信息，输入0和#结束:i,ch");
       scanf("%d,%c",&i,&ch);
   }
   return t;
}/* Create_BiTree1*/
void  Preorder(BTNode *bt)
{/*前序递归遍历*/
    if(bt)
    {
          printf("%c",bt->cdata);
          Preorder(bt->lchild);
        Preorder(bt->rchild);
    }
}/* Preorder*/

void main()
{
    BTNode *g;
    Create_BiTree(&g);
    Preorder(g);
}