1_2_1.cpp

#include<iostream>
#define size 8


struct inode {
	int data;
	struct inode * link;
};
typedef struct inode node_t;
void inq(int);
int deq();
void print_list(node_t * head);
using namespace std;
node_t * head = NULL;
node_t * tail = NULL;

int main() {
	int in = 0;

	while (1) {
		cout << "input number:";
		cin >> in;
		if (in > 0) {
			inq(in);
		}
		else if (in == 0) {
			int out = deq();
			if (out != -1)
				cout << "[" << out << "]" << endl;
		}
		else if (in < 0) {
			cout << "program treminated..." << endl;
			print_list(head);
			return 0;
		}
	}
}
void inq(int x) {

	node_t * n = new node_t;
	n->data = x;
	n->link = NULL;

	if (head == NULL)
	{
		head = n;
		tail = n;
	}
	else {

		tail->link = n;
		tail = n;
	}
}
int deq() {

	if (head == NULL)
	{
		cout << "queue is empty" << endl;
		return -1;
	}

	node_t *tem = head;
	int t = head->data;

	head = head->link;
	if (head == NULL)
		tail = NULL;
	delete tem;
	return t;
}
void print_list(node_t * h) {
	if (h != NULL)
	{
		cout << h->data << " ";
		print_list(h->link);
	}
	else
		cout << endl;

}