队列的链式实现

用链式存储结构，实现教材定义的队列的基本操作。
菜单中包括以下功能：
1.初始化队列，2.销毁队列，3.清空队列，4. 队列判空，5.求队列长度，6.获取队头元素，7.插入一个 元素，8.删除一个元素，9输出所有元素。
要求：自定义的函数中不允许出现提示语和输出语句。

#include <iostream>
using namespace std;


typedef struct Code
{
	struct Code* next;
	int data;
}Code,* List;

typedef struct
{
	Code *front;
	Code *end;
	int length;
}str;

//初始化一个队列
str InistList(str &L)
{
	L.front = L.end = (List)malloc(sizeof(Code));
	if (L.front == NULL)
		exit(OVERFLOW);
	else
	{
		L.front->next = NULL;
		L.length = 0;
	}
	return L;
}

//销毁一个队列
int ListDistory(str &L)
{
	List p = L.front->next;
	free(L.front);
	L.front = NULL;
	L.end = NULL;
	while (true)
	{
		if (p != NULL)
		{
			List q = p;
			p = p->next;
			free(q);
			q = NULL;
		}
		else
			break;
	}
	return true;
}

//清空一个队列
int ClearList(str &L)
{
	List p = L.front->next;
	L.front->data = NULL;
	L.front->next = NULL;
	L.end = L.front;
	L.length = 0;
	while (true)
	{
		if (p != NULL)
		{
			List q = p;
			p = p->next;
			free(q);
			q = NULL;
		}
		else
			break;
	}
	return true;
}

//队列判空
int ListEmpty(str L)
{
	return L.length;
}

//求队列长度
int ListLength(str L)
{
	return L.length;
}

//获取队头元素
int GetHead(str L)
{
	return L.front->data;
}

//插入一个元素
int InsertElem(str& L, int elem)
{
	if (L.length == 0)
	{
		L.front->data = elem;
		L.length++;
		return true;
	}
	List OneElem = NULL;
	OneElem = (List)malloc(sizeof(Code));
	if (OneElem == NULL)
		exit(OVERFLOW);
	else
	{
		OneElem->next = NULL;
		OneElem->data = elem;
		L.end->next = OneElem;
		L.end = OneElem;
		L.length++;
	}
	return true;
}

//删除一个元素
int DeletElem(str &L)
{
	if (L.length == 1)
	{
		int elem = L.front->data;
		L.front->data = NULL;
		L.length--;
		return elem;
	}
	List p = L.front;
	int elem = L.front->data;
	L.front = L.front->next;
	free(p);
	p = NULL;
	L.length--;
	return elem;
}

//输出所有元素
int ElemPrint(str L)
{
	List p = L.front;
	for (int i = 0; i < L.length; i++)
	{
		cout << p->data << " ";
		p = p->next;
	}
	cout << endl;
	return true;
}

int main()
{
	int a,i;
	int count = 0;
	str L;
	while (true)
	{
		cout << "1.初始化队列" << endl;
		cout << "2.销毁队列" << endl;
		cout << "3.清空队列" << endl;
		cout << "4.队列判空" << endl;
		cout << "5.求队列长度" << endl;
		cout << "6.获取队头元素" << endl;
		cout << "7.插入一个元素" << endl;
		cout << "8.删除一个元素" << endl;
		cout << "9.输出所有元素" << endl;
		cout << "输入一个负数退出" << endl;
		cout << "请输入你的选择" << endl;
		cin >> a;
		if (a < 0)
		{
			cout << "已退出" << endl;
			break;
		}
		else if (a > 9 || a == 0)
		{
			cout << "输入错误，请重新输入" << endl;
			continue;
		}
		switch (a)
		{
		case 1:
		{
			if (count == 0)
			{
				L = InistList(L);
				cout << "已成功初始化一个队列" << endl;
				count = 1;
			}
			else
				cout << "队列已存在，请先销毁该链表" << endl;
			break;
		}
		case 2:
		{
			if (count == 1)
			{
				ListDistory(L);
				cout << "已成功销毁一个队列" << endl;
				count = 0;
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		case 3:
		{
			if (count == 1)
			{
				ClearList(L);
				cout << "队列已清空" << endl;
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		case 4:
		{
			if (count == 1)
			{
				i = ListEmpty(L);
				if (i == 0)
					cout << "当前队列为空队列" << endl;
				else
					cout << "当前队列不为空" << endl;
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		case 5:
		{
			if (count == 1)
			{
				i = ListLength(L);
				cout << "当前队列长度为" << i << endl;
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		case 6:
		{
			if (count == 1)
			{
				if (L.length == 0)
				{
					cout << "当前队列为空队列，无队头元素" << endl;
				}
				else
				{
					i = GetHead(L);
					cout << "当前队列队头元素为" << i << endl;
				}
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		case 7:
		{
			if (count == 1)
			{
				cout << "请输入要插入的元素" << endl;
				cin >> i;
				InsertElem(L, i);
				cout << "插入" << i << "后的队列为：";
				ElemPrint(L);
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		case 8:
		{
			if (count == 1)
			{
				if (L.length == 0)
				{
					cout << "该队列为空队列，无法删除元素" << endl;
				}
				else
				{
					i = DeletElem(L);
					cout << "删除" << i << "后的队列为：";
					if (L.length != 0)
						ElemPrint(L);
					else
						cout << "空队列" << endl;
				}
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		case 9:
		{
			if (count == 1)
			{
				if (L.length == 0)
				{
					cout << "该队列为空队列，不能输出元素" << endl;
				}
				else
				{
					cout << "该队列的元素为：" ;
					ElemPrint(L);
				}
			}
			else
			{
				cout << "队列不存在，请先初始化一个队列" << endl;
			}
			break;
		}
		}
		system("pause");
		system("cls");
	}
}