std::priority_queue

场景:

1. 对于一个任务队列，任务的优先级由任务的priority属性指明，这时候就需要优先级越高的先执行。而queue并没有排序功能，这时priority_queue是比较好的选择.

2 对于异步的task也是一样，在不断添加新的task时,当然希望优先级越高的先执行.

解析:

1. 如果需要把优先级最高的先pop,那么comp比较时需要返回false.

代码:

//1.Elements are popped from the "back" of the specific container, 
//which is known as the top of the priority queue.
//2.shall return true if a is considered to go before b 
// in the strict weak ordering the function defines
#include 
  
   
#include 
   
     #include 
    
      #include 
     
       using namespace std; class Task { public: Task(int priority):priority_(priority) { } ~Task(){} int priority_; void DoWork() { cout << "DoWork: " << (int)this << " priority: " << priority_ << endl; } }; class PriorityCompare { public: bool operator()(Task* t1,Task* t2) { return t1->priority_ > t2->priority_; } /* data */ }; int main(int argc, char const *argv[]) { PriorityCompare pc; priority_queue
      
       ,PriorityCompare> tasks(pc); Task t1(1); Task t2(10); Task t3(3); Task t4(1); Task t5(8); Task t6(9); tasks.push(&t1); tasks.push(&t2); tasks.push(&t3); tasks.push(&t4); tasks.push(&t5); tasks.push(&t6); while(!tasks.empty()) { Task* task = tasks.top(); tasks.pop(); task->DoWork(); } return 0; } 
      
     
    
   
  

输出:

DoWork: 2293456 priority: 1
DoWork: 2293444 priority: 1
DoWork: 2293448 priority: 3
DoWork: 2293440 priority: 8
DoWork: 2293436 priority: 9
DoWork: 2293452 priority: 10