优先队列本质就是堆，可自定义比较方式
适配器默认使用vector，也可以使用deque，但deque效率太低

1.greater与less

模拟实现std的两个比较仿函数

	template<class T>
	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;
		}
	};

2.adjust_up()与adjust_down()

堆的向上调整和向下调整

		void adjust_up(size_t child)
		{
			Compare com;
			int parent = (child - 1) / 2;
			while (child > 0)
			{
				if (com(_con[parent], _con[child]))
				{
					std::swap(_con[child], _con[parent]);
					child = parent;
					parent = (child - 1) / 2;
				}
				else
				{
					break;
				}
			}
		}
		void adjust_down(size_t parent)
		{
			Compare com;
			size_t child = parent * 2 + 1;
			while (child < _con.size())
			{
			
				if (child + 1 < _con.size() && com(_con[child], _con[child + 1]))
				{
					++child;
				}


				if (com(_con[parent], _con[child]))
				{
					std::swap(_con[child], _con[parent]);
					parent = child;
					child = parent * 2 + 1;
				}
				else
				{
					break;
				}
			}
		}

3.总代码

namespace mtstd
{
	template<class T>
	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;
		}
	};

	template<class T, class Container = std::vector<T>, class Compare = less<T>>
	class priority_queue
	{
	public:
		void adjust_up(size_t child)
		{
			Compare com;
			int parent = (child - 1) / 2;
			while (child > 0)
			{
				if (com(_con[parent], _con[child]))
				{
					std::swap(_con[child], _con[parent]);
					child = parent;
					parent = (child - 1) / 2;
				}
				else
				{
					break;
				}
			}
		}

		void push(const T& x)
		{
			_con.push_back(x);
			adjust_up(_con.size() - 1);
		}

		void adjust_down(size_t parent)
		{
			Compare com;
			size_t child = parent * 2 + 1;
			while (child < _con.size())
			{
			
				if (child + 1 < _con.size() && com(_con[child], _con[child + 1]))
				{
					++child;
				}


				if (com(_con[parent], _con[child]))
				{
					std::swap(_con[child], _con[parent]);
					parent = child;
					child = parent * 2 + 1;
				}
				else
				{
					break;
				}
			}
		}

		void pop()
		{
			std::swap(_con[0], _con[_con.size() - 1]);
			_con.pop_back();
			adjust_down(0);
		}

		bool empty()
		{
			return _con.empty();
		}

		size_t size()
		{
			return _con.size();
		}

		const T& top()
		{
			return _con[0];
		}

	private:
		Container _con;
	};
}