priority_queue 优先队列

Posted 2020-08-14 KennyRom

优先队列是单向队列的一种，可以按照默认或自定义的一种方式来对队列中的数据进行动态排序

template<class _Ty, class _Container = vector<_Ty>, class _Pr = less<typename _Container::value_type> > //默认以vector为容器的  
class priority_queue  
{   // priority queue implemented with a _Container  
public:  
    typedef _Container container_type;  
    typedef typename _Container::value_type value_type;  
    typedef typename _Container::size_type size_type;  
    typedef typename _Container::reference reference;  
    typedef typename _Container::const_reference const_reference;  
  
    priority_queue() : c(), comp()  
    {   // construct with empty container, default comparator  
    }  
  
    explicit priority_queue(const _Pr& _Pred) : c(), comp(_Pred)  
    {   // construct with empty container, specified comparator  
    }  
  
    priority_queue(const _Pr& _Pred, const _Container& _Cont) : c(_Cont), comp(_Pred)  
    {   // construct by copying specified container, comparator  
        make_heap(c.begin(), c.end(), comp); //参见《STL系列之四 heap 堆的相关函数》  
    }  
  
    template<class _Iter>  
    priority_queue(_Iter _First, _Iter _Last) : c(_First, _Last), comp()  
    {   // construct by copying [_First, _Last), default comparator  
        make_heap(c.begin(), c.end(), comp);  
    }  
  
    template<class _Iter>  
    priority_queue(_Iter _First, _Iter _Last, const _Pr& _Pred) : c(_First, _Last), comp(_Pred)  
    {   // construct by copying [_First, _Last), specified comparator  
        make_heap(c.begin(), c.end(), comp);  
    }  
  
    template<class _Iter>  
    priority_queue(_Iter _First, _Iter _Last, const _Pr& _Pred, const _Container& _Cont) : c(_Cont), comp(_Pred)  
    {   // construct by copying [_First, _Last), container, and comparator  
        c.insert(c.end(), _First, _Last);  
        make_heap(c.begin(), c.end(), comp);  
    }  
  
    bool empty() const  
    {   // test if queue is empty  
        return (c.empty());  
    }  
  
    size_type size() const  
    {   // return length of queue  
        return (c.size());  
    }  
  
    const_reference top() const  
    {   // return highest-priority element  
        return (c.front());  
    }  
  
    reference top()  
    {   // return mutable highest-priority element (retained)  
        return (c.front());  
    }  
  
    void push(const value_type& _Pred)  
    {   // insert value in priority order  
        c.push_back(_Pred);  
        push_heap(c.begin(), c.end(), comp);  
    }  
  
    void pop()  
    {   // erase highest-priority element  
        pop_heap(c.begin(), c.end(), comp);  
        c.pop_back();  
    }  
  
protected:  
    _Container c;   // the underlying container  
    _Pr comp;   // the comparator functor  
}; 

　　

用法：

1、默认用<运算符进行排序

大的先输出

 

2、priority_queue<type, vector<type>, fun<type>>pq;

vector<type>为容器类型

fun<type>为比较函数

 

3、自定义优先级

重载<

struct node
{
    friend bool operator< (node n1, node n2)
    {
        return n1.priority < n2.priority;
    }
    int priority;
    int value;
};