优先级队列（priority queue）就是遵循两个排序规则的集合。首先，具有高优先级的项目在先。第二，具有相同优先级的项目使用先进先出方法来确定其排序。-Priority queue (priority queue) is to follow two collations set. First, a high-priority item first. Second, with the same priority projects using the FIFO method to determine the order.