C++实现priority_queue容器适配器

Posted 2021-05-26 Wecccccccc

代码如下:

#pragma once
#include <iostream>
#include <vector>
using namespace std;

template<typename T>
struct Less
{
	bool operator()(const T &a, const T &b)
	{
		return a < b;
	}
};

template<typename T>
struct Greater
{
	bool operator()(const T &a, const T &b)
	{
		return a > b;
	}
};

template<typename T, typename Container = vector<T>, typename Compare = Less<T>>
class priorityQueue
{
public:

	void shiftDown()
	{
		int parent = 0;
		int child = 2 * parent + 1;
		while (child < con.size())
		{
			if (child + 1 < con.size() && cmp(con[child], con[child + 1]))
			{
				++child;
			}
			if (cmp(con[parent], con[child]))
			{
				swap(con[parent], con[child]);
				parent = child;
				child = 2 * parent + 1;
			}
			else break;
		}
	}

	void shiftUp(int child)
	{
		int parent = (child - 1) / 2;
		while (child > 0)
		{
			if (cmp(con[parent], con[child]))
			{
				swap(con[parent], con[child]);
				child = parent;
				parent = (child - 1) / 2;
			}
			else break;
		}
	}

	void push(const T& val)
	{
		con.push_back(val);
		shiftUp(con.size() - 1);
	}

	void pop()
	{
		swap(con[0], con[con.size() - 1]);
		con.pop_back();
		shiftDown();
	}

	T & top()
	{
		return con.front();
	}

	size_t size() const
	{
		return con.size();
	}

	bool empty() const
	{
		return con.empty();
	}

private:
	Container con;
	Compare cmp;
};

测试代码如下:

#include <iostream>
#include "PriorityQueue.h";
using namespace std;

int main()
{
	priorityQueue<int>pq;
	pq.push(13);
	pq.push(14);
	pq.push(9);
	pq.push(23);
	pq.push(12);
	pq.push(22);
	while (!pq.empty())
	{
		cout << pq.top() << " ";
		pq.pop();
	}
	cout << endl;

	priorityQueue<int, vector<int>, greater<int>> pq1;
	pq1.push(13);
	pq1.push(14);
	pq1.push(9);
	pq1.push(23);
	pq1.push(12);
	pq1.push(22);
	while (!pq1.empty())
	{
		cout << pq1.top() << " ";
		pq1.pop();
	}
	cout << endl;

	class A
	{
	public:
		A(int a = 1):_a(a){}

		bool operator<(const A& a) const
		{
			return _a < a._a;
		}

		bool operator > (const A &a) const
		{
			return _a > a._a;
		}

		int _a;
	};

	priorityQueue<A> pq2;
	pq2.push(A(123));
	pq2.push(A(14));
	pq2.push(A(13));
	pq2.push(A(23));
	pq2.push(A(88));
	pq2.push(A(999));
	while (!pq2.empty())
	{
		cout << pq2.top()._a << " ";
		pq2.pop();
	}
	cout << endl;
	return 0;
}

测试结果: