数据结构——链队列

/*------链队列基本操作-------*/
/*
front指针指向头结点（第一个结点的前一个）
rear指针指向最后一个结点
*/
#include<iostream>
#include<stdlib.h>
using namespace std;

#define OK 1
#define ERROR -1
#define OVERFLOW -2

typedef int Status;
typedef int QElemType;

#define MAXSIZE 100

typedef struct Qnode {
	QElemType data;
	struct Qnode* next;
}Qnode, * QueuePtr;

typedef struct {
	QueuePtr front;
	QueuePtr rear;
}LinkQueue;

Status InitLQueue(LinkQueue& Q) {
	Q.front = new Qnode;
	if (!Q.front) exit(OVERFLOW);
	Q.rear = Q.front;
	Q.front->next = NULL;
	return OK;
}

// 判断链队列是否为空
bool LQueueEmpty(LinkQueue Q) {
	return (Q.front == Q.rear);
}

// 入队
Status PushLQueue(LinkQueue& Q, QElemType e) {
	QueuePtr q;
	q = new Qnode;
	if (!q)  exit(OVERFLOW);
	q->data = e;
	q->next = NULL;
	Q.rear->next = q;
	Q.rear = q;
	return OK;
}

// 出队
Status PopLQueue(LinkQueue& Q, QElemType& e) {
	QueuePtr q;
	if(LQueueEmpty(Q)) return ERROR;
	q = Q.front->next;
	e = q->data;
	Q.front->next = q->next;
	if (Q.rear == q) Q.rear = Q.front;
	delete q;
	return OK;
}

// 销毁链队列
Status DestroyQueue(LinkQueue& Q) {
	while (Q.front) {
		Q.rear = Q.front->next;
		delete Q.front;
		Q.front = Q.rear;
	}
	return OK;
}

// 获取队头元素
Status GetHead(LinkQueue Q, QElemType& e) {
	if (LQueueEmpty(Q)) return ERROR;
	e = Q.front->next->data;
	return OK;
}

// 创建链队列
void CreateLQueue(LinkQueue& Q, int m) {
	QElemType e;
	for (int i = 1; i <= m; i++) {
		cout << "请输入第" << i << "个元素: ";
		cin >> e;
		PushLQueue(Q, e);
	}
}

// 输出链队列
void OutPut(LinkQueue Q) {
	QueuePtr q;
	q = new Qnode;
	q = Q.front->next;
	while (q) {
		cout << q->data << " ";
		q = q->next;
	}
	cout << endl;
}

int main()
{
	// 测试代码
	LinkQueue Q;
	int m;
	QElemType e;
	InitLQueue(Q);
	cout << "请输入链队列的长度: ";
	cin >> m;
	CreateLQueue(Q, m);
	cout << "链队列元素为: ";
	OutPut(Q);

	GetHead(Q, e);
	cout << "队头元素为: " << e << endl;

	cout << "请输入入队元素: ";
	cin >> e;
	PushLQueue(Q, e);
	cout << "链队列元素为: ";
	OutPut(Q);

	PopLQueue(Q, e);
	cout << "出列元素为: " << e << endl;
	cout << "链队列元素为: ";
	OutPut(Q);

	return 0;
}

请输入链队列的长度: 3

请输入第1个元素: 1

请输入第2个元素: 2

请输入第3个元素: 3

链队列元素为: 1 2 3

队头元素为: 1

请输入入队元素: 4

链队列元素为: 1 2 3 4

出队元素为: 1

链队列元素为: 2 3 4