填空题

[说明] 假设二叉树采用链式存储方式存储，编写一个后序遍历二叉树的非递归方式。
Void postorder (btree * B)
btree * stack [m0] , *p;
int tag [m0], top =0;
p=b;
do

while (p! =NULL)

top+ +;
(1)
tag [top] =0;
p =p- ＞left;

if (top ＞0)

(2)
if (tag[top3 = =1)

(3)
print ("%d", p- ＞data);

if(top＞0)

(4)
tag [top] = 1;


while (p! = NULL && top ! =0)