[C/C++標準庫]_[初級]_[優先隊列priority_queue的使用]

std::priority_queue
場景:

1. 對於一個任務隊列，任務的優先級由任務的priority屬性指明，這時候就須要優先級越高的先執行。而queue並無排序功能，這時priority_queue是比較好的選擇.

2 對於異步的task也是同樣，在不斷添加新的task時,固然但願優先級越高的先執行.

解析:

1. 若是須要把優先級最高的先pop,那麼comp比較時須要返回false.

代碼:

//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;
}
 

輸出:

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

參考: http://www.cplusplus.com/reference/queue/priority_queue/
--------------------- 
做者：infoworld 
來源：CSDN 
原文：https://blog.csdn.net/infoworld/article/details/24941961 
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