8

This site suggests that if I want to reverse-order my priority queues, the following code is what I should use:

#include <iostream>
#include <queue>
using namespace std;

class mycomparison{
    bool reverse;
  public:
    mycomparison(const bool &revparam=false) {reverse=revparam;}
    bool operator() (const int &lhs, const int &rhs) const {
      if (reverse) return (lhs>rhs);
      else         return (lhs<rhs);
    }
};

int main (){
  int myints[]= {10,60,50,20};

  priority_queue<int, vector<int>, mycomparison(true)> first;

  return 0;
}

This bothers me:

  • I have to specify the storage class in my constructor.
  • I have created a class whose only purpose is to be passed to the priority queue.

Is there a more elegant or less verbose way of reverse-sorting a priority queue?

4

3 回答 3

28

您无法避免指定存储容器，但可以避免编写自己的函子：

priority_queue<int, vector<int>, std::greater<int> > first;
于 2013-03-26T20:55:25.147 回答
1

如果您想要灵活性而不必定义任何类，则可以使用比较器std::function>的类型：

#include <functional>

int main ()
{
    int myints[]= {10,60,50,20};

    // Use this is a the type of your comparator
    typedef std::function<bool(int, int)> comp_type;

    // Priority queue using operator < for ordering
    priority_queue<int, vector<int>, comp_type> first(std::less<int>());

    // ...

    // Priority queue using operator > for ordering
    priority_queue<int, vector<int>, comp_type> second(std::greater<int>());

    // ...

    return 0;
}
于 2013-03-26T21:01:56.140 回答
0

在反转结构的优先级队列时，我找到了更简单的解决方案。我从那里修改了解决方案：stl priority_queue of C++ with struct

struct leaf
{
int symbol;
double probability;
bool operator < (const leaf &o) const 
    {
        return probability > o.probability; // here just reversed the operator
    }
};

priority_queue <leaf> leafs_queue; //queue already reversed
于 2020-11-03T09:43:40.907 回答