在优先级队列中配对 [英] Pair inside priority queue

问题描述

我尝试在优先级队列中存储对，我使用比较每对的第二个值的比较函数。

I am trying to store pairs in priority queue and I am using a compare function that compares second value of each pair.

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

class CompareDist
{
public:
    bool operator()(pair<int,int> n1,pair<int,int> n2) {
        return n1.second>n2.second;
    }
};
int main()
{
    priority_queue<pair<int,int>,CompareDist> pq;
}

当我编译这个文件时会出现错误

When I compile this I get an error

error: no type named ‘value_type’ in ‘class CompareDist’

$ b $

推荐答案

这是 href =http://en.cppreference.com/w/cpp/container/priority_queue> priority_queue 如下所示：

This is what priority_queue looks like:

template<
    class T,
    class Container = std::vector<T>, 
    class Compare = std::less<typename Container::value_type>
> class priority_queue;

换句话说， CompareDist 第三参数，第二个参数应为容器（其具有 value_type ），如下所示：

In other words, CompareDist should be the third argument and the second argument should be the container (which has value_type), like the following:

priority_queue<pair<int,int>,vector<pair<int,int>>,CompareDist> pq;

注意， priority_queue 称为容器适配器。另一个容器用作底层容器，priority_queue具有访问它的特殊成员函数。容器适配器的另一个示例是std :: stack。

Notice also, that priority_queue is what is called a "container adaptor". Another container is used as the underlying container and the priority_queue has special members functions for accessing it. Another example of a container adaptor would be std::stack.

这篇关于在优先级队列中配对的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！