【C++航海王：追寻罗杰的编程之路】priority_queue(优先队列) | 容器适配器你知道哪些？

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <iostream>
#include <vector>
#include <queue>
#include <functional>
using namespace std;
 
void TestPriorityQueue()
{
  vector<int> v{ 3,2,7,6,0,4,1,9,8,5 };
 
  priority_queue<int> q1;
  for (auto& e : v)
    q1.push(e);
  cout << q1.top() << endl;
 
  // 如果要创建小堆，将第三个模板参数换成greater比较方式
  priority_queue<int, vector<int>, greater<int>> q2(v.begin(), v.end());
  cout << q2.top() << endl;
}
 
int main()
{
 
  TestPriorityQueue();
 
  return 0;
}

class Date
{
public:
  Date(int year = 1900, int month = 1, int day = 1)
    : _year(year)
    , _month(month)
    , _day(day)
  {}
 
  bool operator<(const Date& d)const
  {
    return (_year < d._year) ||
      (_year == d._year && _month < d._month) ||
      (_year == d._year && _month == d._month && _day < d._day);
  }
 
  bool operator>(const Date& d)const
  {
    return (_year > d._year) ||
      (_year == d._year && _month > d._month) ||
      (_year == d._year && _month == d._month && _day > d._day);
  }
 
  friend ostream& operator<<(ostream& _cout, const Date& d)
  {
    _cout << d._year << "-" << d._month << "-" << d._day;
    return _cout;
  }
 
private:
  int _year;
  int _month;
  int _day;
};
 
void TestPriorityQueue()
{
  // 大堆，需要用户在自定义类型中提供<的重载
  priority_queue<Date> q1;
  q1.push(Date(2024, 10, 29));
  q1.push(Date(2024, 10, 28));
  q1.push(Date(2024, 10, 30));
  cout << q1.top() << endl;
 
  // 如果要创建小堆，需要用户提供>的重载
  priority_queue<Date, vector<Date>, greater<Date>> q2;
  q2.push(Date(2024, 10, 29));
  q2.push(Date(2024, 10, 28));
  q2.push(Date(2024, 10, 30));
  cout << q2.top() << endl;
}

#include <iostream>
#include <vector>
using namespace std;
 
// priority_queue--->堆
namespace fyd
{
  template<class T>
  struct less
  {
    bool operator()(const T& left, const T& right)
      return left < right;
  };
 
  template<class T>
  struct greater
  {
    bool operator()(const T& left, const T& right)
      return left > right;
  };
 
  template<class T, class Container = std::vector<T>, class Compare = less<T>>
  class priority_queue
  {
  public:
    // 创造空的优先级队列
    priority_queue() : c() {}
 
    template<class Iterator>
    priority_queue(Iterator first, Iterator last)
      : c(first, last)
    {
      // 将c中的元素调整成堆的结构
      int count = c.size();
      int root = ((count - 2) >> 1);
      for (; root >= 0; root--)
        AdjustDown(root);
    }
 
    void push(const T& data)
    {
      c.push_back(data);
      AdjustUP(c.size() - 1);
    }
 
    void pop()
    {
      if (empty())
        return;
 
      swap(c.front(), c.back());
      c.pop_back();
      AdjustDown(0);
    }
 
    size_t size()const
    {
      return c.size();
    }
 
    bool empty()const
    {
      return c.empty();
    }
 
    // 堆顶元素不允许修改，因为：堆顶元素修改可以会破坏堆的特性
    const T& top()const
    {
      return c.front();
    }
  private:
    // 向上调整
    void AdjustUP(int child)
    {
      int parent = ((child - 1) >> 1);
      while (child)
      {
        if (Compare()(c[parent], c[child]))
        {
          swap(c[child], c[parent]);
          child = parent;
          parent = ((child - 1) >> 1);
        }
        else
          return;
      }
    }
 
    // 向下调整
    void AdjustDown(int parent)
    {
      size_t child = parent * 2 + 1;
      while (child < c.size())
      {
        // 找以parent为根的较大的孩子
        if (child + 1 < c.size() && Compare()(c[child], c[child + 1]))
          child += 1;
 
        // 检测双亲是否满足情况
        if (Compare()(c[parent], c[child]))
        {
          swap(c[child], c[parent]);
          parent = child;
          child = parent * 2 + 1;
        }
        else
          return;
      }
    }
  private:
    Container c;
  };
}

#include<deque>
 
namespace fyd
{
  template<class T, class Con = deque<T>>
  //template<class T, class Con = vector<T>>
  //template<class T, class Con = list<T>>
  class stack
  {
  public:
    stack() {}
    void push(const T& x) { _c.push_back(x); }
    void pop() { _c.pop_back(); }
    T& top() { return _c.back(); }
    const T& top()const { return _c.back(); }
    size_t size()const { return _c.size(); }
    bool empty()const { return _c.empty(); }
  private:
    Con _c;
  };
}

#include<deque>
#include <list>
 
namespace fyd
{
  template<class T, class Con = deque<T>>
  //template<class T, class Con = list<T>>
  class queue
  {
  public:
    queue() {}
    void push(const T& x) { _c.push_back(x); }
    void pop() { _c.pop_front(); }
    T& back() { return _c.back(); }
    const T& back()const { return _c.back(); }
    T& front() { return _c.front(); }
    const T& front()const { return _c.front(); }
    size_t size()const { return _c.size(); }
    bool empty()const { return _c.empty(); }
  private:
    Con _c;
  };
}