链式队列的实现

#include <iostream>
#include <cstdlib>

using namespace std;

typedef struct node{
	int data;
	struct node* next;
}Node;

typedef struct{
	Node *front;
	Node *rear;
}Queue;

//新建队列
void initQueue(Queue &Q){
	Q.front = Q.rear = new Node;
	Q.front -> next = NULL;
}

//队列判空
bool isEmptyQueue(Queue &Q){
	
	if(NULL == Q.front){    //此时队列被销毁
		exit(1);
	}
	if(Q.front == Q.rear)    
		return true;	//队列为空
		
	return false;
}

//入队
void enterQueue(Queue &Q, int element){
	Node *p = new Node;
	p -> next = NULL;
	p -> data = element;
	Q.rear -> next = p;
	Q.rear = p;
}

//出队
int deQueue(Queue &Q){
	int  outElement;
	if(isEmptyQueue(Q)){
		exit(1);
	}
	
	Node *p = Q.front -> next;
	outElement = p -> data;
	
	Q.front -> next = p -> next;
	if(Q.rear == p){
		Q.rear = Q.front;
	}
	delete p;
	
	return outElement;
}

//求队列长度
int getLength(Queue &Q){
	Node* p1 = Q.front;
	Node* p2 = Q.rear;
	int length = 0;
	
	while(p1 != p2){
		p1 = p1 -> next;
		length++;
	}

	return length;
}

//访问头部
int getHead(Queue & Q){
	if(isEmptyQueue(Q)){
		exit(1);
	}
	return Q.front -> next -> data;
}

//清空队列
void clearQueue(Queue &Q){
	while(!isEmptyQueue(Q)){
		deQueue(Q);
	}
}

//销毁队列
void destroyQueue(Queue &Q){
	clearQueue(Q);
	delete Q.front;
	Q.front = Q.rear = NULL;
}

int main(){
	Queue Q;
	initQueue(Q);
	cout << getLength(Q) << endl;

	for(int i = 1; i <= 10; ++i){
		enterQueue(Q, i);
	}
	cout << getHead(Q) << endl;
	cout << getLength(Q) << endl;

	while(!isEmptyQueue(Q)){
		cout << deQueue(Q) << " ";
	}
	cout << endl;

	if(!isEmptyQueue(Q))
		cout << "Yes" << endl;
	else
		cout << "NO" << endl;

	clearQueue(Q)
	
	if(!isEmptyQueue(Q))
		cout << "Yes" << endl;
	else
		cout << "NO" << endl;
		
	destroyQueue(Q);
	
	return 0;
}