[C/C++标准库]_[初级]_[优先队列priority_queue的使用]

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 <stdlib.h>
#include <iostream>
#include <queue>
#include <vector>
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<Task*,std::vector<Task*>,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

参考: http://www.cplusplus.com/reference/queue/priority_queue/