c实现哲学家进餐问题。WINDOWS下。

// 解决哲学家就餐问题
// 每个哲学家可用一个线程来模拟。
// 设有5个哲学家，5只筷子，每个哲学家吃饭时间为一个随机值，哲学家吃饭后的思考时间也是一个随机值。
#include <Windows.h>
#include <iostream>
#include <cstdio>
#include <stdlib.h>
#include <time.h>
/*
（1）奇数号的哲学家先拿起右边的筷子再拿起左边的筷子。

（2）偶数号哲学家先拿起左边的筷子，再拿起右边的筷子。

（3）如果哲学家抢到一只筷子，在抢占另一只筷子时失败，则要放弃已经抢占到的资源。

（4）左右两边都抢到筷子的哲学家，吃完放后释放资源。*/
using namespace std;

HANDLE chop[5];
HANDLE ph[5];
HANDLE mutex;
int nums=0;

int random()
{
return rand()%100+20;
}
void eating(int id)
{
int num=random();
Sleep(num);
printf("\t\t\t哲学家%d号吃了%d秒\n",id,num);
}

DWORD WINAPI phthread(LPVOID param){
nums++;
int id=nums;
int lc=id-1;
int rc=id%5;
int times=0;
int ret1,ret2;
while(true)
{
Sleep(100);
if (times>=2)
break;
if (id % 2 == 0)
{
ret1 = WaitForSingleObject(chop[lc], 0);
if (ret1 == WAIT_OBJECT_0)
{
ret2 = WaitForSingleObject(chop[rc], 0);
if (ret2 == WAIT_OBJECT_0)
{
WaitForSingleObject(mutex,INFINITE);
printf("哲学家%d号拿到两只筷子开始吃第%d顿饭。\n", id,times+1);
ReleaseMutex(mutex);
times++;
WaitForSingleObject(mutex,INFINITE);
eating(id);
ReleaseMutex(mutex);
WaitForSingleObject(mutex,INFINITE);
printf("\t\t\t哲学家%d号吃完两顿饭啦，放下筷子。\n", id);
ReleaseMutex(mutex);
ReleaseSemaphore(chop[rc], 1, NULL);
}
ReleaseSemaphore(chop[lc], 1, NULL);
}
}
else
{
ret1 = WaitForSingleObject(chop[rc], 0);
if (ret1 == WAIT_OBJECT_0)
{
ret2 = WaitForSingleObject(chop[lc], 0);
if (ret2 == WAIT_OBJECT_0)
{
WaitForSingleObject(mutex,INFINITE);
printf("哲学家%d号拿到两只筷子开始吃%d顿饭。\n", id,times+1);
ReleaseMutex(mutex);
times++;
WaitForSingleObject(mutex,INFINITE);
eating(id);
ReleaseMutex(mutex);
WaitForSingleObject(mutex,INFINITE);
printf("\t\t\t哲学家%d号吃完两顿饭啦，放下筷子。\n", id);
ReleaseMutex(mutex);
ReleaseSemaphore(chop[lc], 1, NULL);
}
ReleaseSemaphore(chop[rc], 1, NULL);
}
}
WaitForSingleObject(mutex,INFINITE);
ReleaseMutex(mutex);
}
printf("=======哲学家%d吃饱了然后离开了。=======\n",id);
return 0;

}

int main()
{
srand((unsigned)time(0));
mutex = CreateMutex(NULL, false, NULL);
for (int i = 0; i < 5; ++i)
{
chop[i]=CreateSemaphore(NULL,1,1,NULL);
}
for (int i = 0; i < 5; ++i)
{
int j = i + 1;
ph[i] = CreateThread(NULL, 0, phthread,NULL, 0, NULL);
}

Sleep(10000);//释放句柄
for (int i = 0; i < 5; ++i)
{
CloseHandle(ph[i]);
CloseHandle(chop[i]);
}
CloseHandle(mutex);
Sleep(500);
system("pause");
return 0;
}