利用信号量方法进行哲学家就餐问题的死锁避免，把哲学家分为三种状态，思考，饥饿，进食，仅当一个哲学家左右两边的筷子都可用时，才允许他拿筷子，并且一次拿到两只筷子，否则不拿-Use semaphores method dining philosophers problem of deadlock avoidance, the philosopher into three states, thinking, hunger, eating only when both sides of a philos