算法习题34：生产者消费者队列（多线程编程）

实现一个队列。
队列的应用场景为：

一个生产者线程将int类型的数入列，一个消费者线程将int类型的数出列

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这道题比较容易，就是一个队列的实现，

这里我用面向对象的结构来写，一个Queue类有生产和消费的方法，里面内部结构是队列

这里我用的是g++编译环境

用的库是POSIX兼容的

就是生成两个线程然后执行消费生产行为 ，这里需要用到一个锁（互斥量）

但是这个程序运行多次发现有时候会陷入死循环，不知是不是发生了死锁，希望有人能指出问题所在

找到原因了！

是我这里的队列出了问题，Consume()函数

如果刚好尾部与头部相遇的时候，我没有判断，仍然执行rear = reae->next;

这里没错，然后我执行了delete temp；也没错，可是front呢？他仍然指向被释放的那块资源，所以这里就出现问题了

Consume改程如下

int Consume(){if(rear == NULL)return -1;size--;int result = rear->value;Node* temp = rear;//这一步很重要/* * 如果这个时候刚好到达尾部，那么必须清空 */if(rear == front){rear = NULL;front = NULL;}else{rear = rear->next;}delete temp;return result;}

我就不直接在源程序上改动了，参考的朋友希望你们注意下这个问题！

//============================================================================// Name        : QueueProducerAndConsumer.cpp// Author      : YLF// Version     :// Copyright   : Your copyright notice// Description : Hello World in C++, Ansi-style//============================================================================#include <iostream>#include <pthread.h>using namespace std;#define MAX 50struct Node{int value;Node* next;};class Queue{private:Node* front;Node* rear;int size;public:Queue(){front = NULL;rear = NULL;size = 0;}void Produce(int value){size++;Node* p = new Node();p->value = value;p->next = NULL;if(front == NULL){rear = p;}elsefront->next = p;front = p;}int Consume(){if(rear == NULL)return -1;size--;int result = rear->value;Node* temp = rear;rear = rear->next;delete temp;return result;}int getSize(){return size;}};int nProduce = 0;int nConsume = 0;pthread_mutex_t mutex;void* Producer(void* attr){Queue *queue = (Queue*)attr;while(nProduce < MAX){pthread_mutex_lock(&mutex);cout<<"Producer:"<<nProduce<<endl;queue->Produce(nProduce);nProduce++;pthread_mutex_unlock(&mutex);}}void* Consumer(void* attr){Queue* queue = (Queue*)attr;while(nConsume < MAX){pthread_mutex_lock(&mutex);int temp = queue->Consume();if(temp != -1){cout<<"Consumer:"<<temp<<endl;nConsume++;}pthread_mutex_unlock(&mutex);}}int main() {Queue *queue = new Queue();pthread_t producer_pthread, consumer_pthread;pthread_mutex_init(&mutex, NULL);pthread_create(&producer_pthread,NULL,Producer,queue);pthread_create(&consumer_pthread,NULL,Consumer,queue);pthread_join(producer_pthread,NULL);pthread_join(consumer_pthread,NULL);pthread_mutex_destroy(&mutex);return 0;}

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