详解C++模拟实现priority_queue(仿函数)

#include <vector>
namespace QBL
{
	template<class T>//仿函数,本质就是运算符重载
	class less
	{
	public:
		bool operator()(const T& x, const T& y)
		{
			return x < y;
		}
	};
	template<class T>
	class greater
	{
	public:
		bool operator()(const T& x, const T& y)
		{
			return x > y;
		}
	};
	//仿函数默认传小于，则是大堆
	//less这点库里面也是和人的直觉是反着的，明明是less，却是大堆
	template<class T, class Container = vector<T>, class Compare = less<T>>
	class priority_queue
	{
	public:
		void adjust_up(size_t child)
		{
			int parent = (child - 1) / 2;
			while (child > 0)
			{
				//if (_con[child] > _con[parent])
				//if (_con[parent] < _con[child])
				if(Compare()(_con[parent], _con[child]))
				{
					swap(_con[child], _con[parent]);
					child = parent;
					parent = (child - 1) / 2;
				}
				else
				{
					break;
				}
			}
		}
		void adjust_down(size_t parent)
		{
			size_t child = parent * 2 + 1;
			while (child < _con.size())
			{
				if (child + 1 < _con.size() && Compare()(_con[child], _con[child + 1]))
					++child;
				//if (_con[child] > _con[parent])
				if(Compare()(_con[parent], _con[child]))
				{
					swap(_con[child], _con[parent]);
					parent = child;
					child = parent * 2 + 1;
				}
				else
				{
					break;
				}
			}
		}
		void push(const T& val)
		{
			_con.push_back(val);
			adjust_up(_con.size() - 1);
		}
		void pop()//删除堆顶
		{
			swap(_con[0], _con[_con.size() - 1]);
			_con.pop_back();
			adjust_down(0);
		}
		const T& top()
		{
			return _con[0];
		}
		bool empty()
		{
			return _con.empty();
		}
		size_t size()
		{
			return _con.size();
		}
	private:
		Container _con;
	};
}

class ComparePDate
{
public:
	bool operator()(const Date* x, const Date* y)
	{
		return *x < *y;
	}
};

struct goods
{ 
	string _name;//名字
	double _price;//价格
	int _evaluate;//评价
	goods(const char* str, double price, int evaluate)
		:_name(str)
		, _price(price)
		, _evaluate(evaluate)
	{}
};
struct ComparePriceLess
{
	bool operator()(const goods& gl, const goods& gr)
	{
		return gl._price < gr._price;
	}
};
struct ComparePriceGreater
{
	bool operator()(const goods& gl, const goods& gr)
	{
		return gl._price > gr._price;
	}
};
struct CompareEvaluateLess
{
	bool operator()(const goods& gl, const goods& gr)
	{
		return gl._evaluate < gr._evaluate;
	}
};
struct CompareEvaluateGreater
{
	bool operator()(const goods& gl, const goods& gr)
	{
		return gl._evaluate > gr._evaluate;
	}
};
int main()
{
	vector<goods> gs = { {"苹果",3.1,5},{"香蕉",2.1,4} ,{"菠萝",1.1,3} ,{"葡萄",4.1,2} };
	sort(gs.begin(), gs.end(), ComparePriceLess());//将仿函数的匿名对象做参数传入，就是我们的比较方式
	sort(gs.begin(), gs.end(), ComparePriceGreater());
	sort(gs.begin(), gs.end(), CompareEvaluateLess());
	sort(gs.begin(), gs.end(), CompareEvaluateGreater());
	return 0;
}