typedef struct
{
    stacknode Elem[maxsize];
    int top;
}SqStack;

void PostOrderUnrec(Bitree t)
{
    SqStack s;
    stacknode x;
    StackInit(s);
    p=t;
   
    do
    {
        while (p!=null)        //遍历左子树
        {
            x.ptr = p;
            x.tag = L;         //标记为左子树
            push(s,x);
            p=p->lchild;
        }
   
        while (!StackEmpty(s) && s.Elem[s.top].tag==R) 
        {
            x = pop(s);
            p = x.ptr;
            visite(p->data);   //tag为R，表示右子树访问完毕，故访问根结点      
        }
       
        if (!StackEmpty(s))
        {
            s.Elem[s.top].tag =R;     //遍历右子树
            p=s.Elem[s.top].ptr->rchild;       
        }   
    }while (!StackEmpty(s));
}//PostOrderUnrec