C++优先队列自定义排序总结

大家好，欢迎来到IT知识分享网。

一、优先队的使用：

二、基本数据类型：

priority_queue<int> q;//默认是从大到小

priority_queue<int, vector<int> ,less<int> >q;//从大到小排序

priority_queue<int, vector<int>, greater<int> >q;//从小到大排序

三、自定义类型:
第1种：

struct Node
{ 
   
	char data;
	int weight;
	Node(char _data, int _weight)
	{ 
   
		data = _data;
		weight = _weight;
	}
};

(1)weight大的优先级高 :

struct cmp1
{ 
   
	bool operator () (const Node &a, const Node &b)		  
	{ 
   
		return a.weight < b.weight;			
	}
};

构造优先队列：

priority_queue< Node, vector<Node>, cmp1> q1;

(2)weight小的优先级高

struct cmp2
{ 
   
	bool operator()(const Node &a, const Node &b)		  
	{ 
   
		return a.weight > b.weight;			
	}
};

构造优先队列：

priority_queue<Node,vector<Node>,cmp2> q2;

第2种：
重载 < 运算符
(1)weight大的优先

struct Node2 
{ 
   
	char data;
	int weight;
	Node2(char _data, int _weight)
	{ 
   
		data = _data;
		weight = _weight;
	}
	friend bool operator < (const Node2 &a,const Node2 &b)
	{ 
   
		return a.weight < b.weight; 		
	} 
};

构造优先队列：

priority_queue<Node2> q3;

（2)weight小的优先

struct Node3 
{ 
   
	char data;
	int weight;
	Node3(char _data, int _weight)
	{ 
   
		data = _data;
		weight = _weight;
	}
	friend bool operator < (const Node3 &a,const Node3 &b)
	{ 
   
		return a.weight > b.weight; 
	} 
};

构造优先队列：

priority_queue<Node3> q4;

test代码：

#include<iostream>
#include<vector>
#include<queue>
using namespace std; 

struct Node
{ 
   
	char data;
	int weight;
	Node(char _data, int _weight)
	{ 
   
		data = _data;
		weight = _weight;
	}
};
struct cmp1
{ 
   

	bool operator () (const Node &a, const Node &b)		  
	{ 
   
		return a.weight < b.weight;			//大的优先级高 
	}
}; 
struct cmp2
{ 
   
	bool operator()(const Node &a, const Node &b)		  
	{ 
   
		return a.weight > b.weight;			//小的优先级高 
	}
};
bool cmp(const Node &a,const Node &b)
{ 
   
	return a.weight > b.weight;
}
struct Node2 
{ 
   
	char data;
	int weight;
	Node2(char _data, int _weight)
	{ 
   
		data = _data;
		weight = _weight;
	}
	friend bool operator < (const Node2 &a,const Node2 &b)
	{ 
   
		return a.weight < b.weight; 
	} 
};
struct Node3 
{ 
   
	char data;
	int weight;
	Node3(char _data, int _weight)
	{ 
   
		data = _data;
		weight = _weight;
	}
	friend bool operator < (const Node3 &a,const Node3 &b)
	{ 
   
		return a.weight > b.weight; 
	} 
};
int main()
{ 
   
	string values = "ABCDEF";
	vector<int> weights = { 
   1,2,3,4,5,6};
	priority_queue< Node, vector<Node>, cmp1> q1;
	for(int i = 0; i < values.length(); i++)
	{ 
   
		Node newNode(values[i],weights[i]); 
		q1.push(newNode);
	}
	cout<<"优先队列q1的第一个元素是: "<<q1.top().data<<endl;
	
	priority_queue<Node,vector<Node>,cmp2> q2;
	for(int i = 0; i < values.length(); i++)
	{ 
   
		Node newNode(values[i],weights[i]); 
		q2.push(newNode);
	}
	cout<<"优先队列q2的第一个元素是: "<<q2.top().data<<endl;
	
	priority_queue<Node2> q3;
	for(int i = 0; i < values.length(); i++)
	{ 
   
		Node2 newNode(values[i],weights[i]); 
		q3.push(newNode);
	}
	cout<<"优先队列q3的第一个元素是: "<<q3.top().data<<endl;
	
	priority_queue<Node3> q4;
	for(int i = 0; i < values.length(); i++)
	{ 
   
		Node3 newNode(values[i],weights[i]); 
		q4.push(newNode);
	}
	cout<<"优先队列q4的第一个元素是: "<<q4.top().data<<endl;
}

运行截图:

更新:

priority_queue< pair<double,int>,
			   	vector<pair<double,int> >,
			   	greater<pair<double,int> > > pq;	//first小的优先
priority_queue< pair<double,int>,
			   	vector<pair<double,int> >,
			   	less<pair<double,int> > > pq;	//first大的优先

first小的优先

class cmp
{ 
   
public:
	bool operator()(pair<double,int> x, pair<double,int> y)
	{ 
   
		return x.first > y.first;
	}
};			   	

first大的优先

class cmp
{ 
   
public:
	bool operator()(pair<double,int> x, pair<double,int> y)
	{ 
   
		return x.first < y.first;
	}
};