Multiple Comparisons in a C++ Priority Queue

We know that the priority queue is the same with the first in, first out functionality, but some priority is attached to its basic implementation. In the C++ standard template library priority queue, we implemented it easily with a simple C++ code snippet and as a container. Here, we will see the Multiple comparisons in a C++ priority queue with its code supported by comments to understand their relevant outputs better.

C++ Code

// here we are writing down the C++ programming language code
// to demonstrate the concept of Multiple comparisons in a C++ 
// priority queue?
#include <bits/stdc++.h>
using namespace std;

// this is the basic template to implement the priority queue 
// written as void function without any return type as i
// general, it prints the heap, again and again, any data type
template <class T>
void printQueue(T& q)
{
    // simple while loop to implement the priority queue
	while (q.empty() == false) {
		cout << q.top() << " ";
		q.pop();
	}
	cout << endl;
}

// this is the basic priority queue property to sort in the 
// form of smallest to highest to the queue
void samplepriorityqueue()
{
	priority_queue<int, vector<int>, greater<int> > pq;
	for (int i = 1; i < 13; i++) {
		pq.push(i);
	}
	printQueue(pq);
}

// Here we are using the lambda comparator function
// to sort given priority queue in ascending order
void samplepriorityqueue1()
{
	auto compare = [](int left, int right) {
		return left < right;
	};
	priority_queue<int, vector<int>, decltype(compare)> pq(
		compare);
	for (int i = 1; i < 13; i++) {
		pq.push(i);
	}
	printQueue(pq);
}


// the struct keyword helps us with implementing the mycmp
// sorting the priority queue, this function has a flexibility 
// extend to various useful features 
struct mycmp {
	bool operator()(int a, int b)
	{
		return a > b;
	}
};
// below void function is the simple code snippet to implement
// the priority queue number two
void samplepriorityqueue2()
{
	priority_queue<int, vector<int>, mycmp> pq;
	// simple for the loop code snippet to run the loop pushing
	// the elements to the priority queue
	for (int i = 1; i < 13; i++) {
		PQ.push(i);
	}
	printQueue(pq);
}

// The main driver code functionality starts from here
int main()
{
    // the driver contains nothing but only function calls
    // which implements the priority queue and prints the 
    // output on our display screens
	samplepriorityqueue();
	samplepriorityqueue1();
	samplepriorityqueue2();
	return 0;
}

Output:

1 2 3 4 5 6 7 8 9 10 11 12 
12 11 10 9 8 7 6 5 4 3 2 1 
1 2 3 4 5 6 7 8 9 10 11 12

C++ Code

// here we are writing down the c++ programming language code
// to demonstrate the concept of Multiple comparisons in a C++ 
// priority queue?
#include <bits/stdc++.h>
using namespace std;

// Structure of a user-defined data structure
struct jobs {
public:
	int priority;
	int processing;
	int arrival time;
	int proccessing_time;
	string job;
	jobs(int priority1, int processing1, int arrivaltime1,
		int proccessing_time1, string s1)
	{
		this->priority = priority1;
		this->processing = processing1;
		this->arrivaltime = arrivaltime1;
		this->proccessing_time = proccessing_time1;
		this->job = s1;
	}
};



// to tackle the processing time, we sort the priority queue
// let us say if the priority queue is similar and we have sorted 
// it in order of increasing to decreasing in the case of the same 
// priority if that is not the case, we have to sort it in the 
// ascending order depending on the priority thrown at us!
struct compare {
	bool operator()(jobs a, jobs b)
	{
		if (a.priority == b.priority) {
			return a.processing < b.processing;
		}
		return a.priority > b.priority;
	}
};

// The main driver code functionality starts from here
int main()
{
	priority_queue<jobs, vector<jobs>, compare> pq;
	// simple for loop to implement the priority queue named jobs
	for (int i = 0; i < 10; i++) {
		jobs a(rand() % 11, i + 1, rand() % 3 + i,
			rand() % 5 + 3, "my_work_day_job_is" + to_string(i));
		PQ.push(a);
	}

	while (pq.empty() == false) {
		jobs b = PQ.top();
		PQ.pop();
		  // the driver contains the while loop 
         // which implements the priority queue and prints the 
        // output on our display screens

		cout << b.priority << " " << b.processing << " "
			<< b.arrivaltime << " " << b.proccessing_time
			<< " " << b.job << endl;
	}
	return 0;
}

Output:

0 9 10 5 my_work_day_job_is8
0 8 7 6 my_work_day_job_is7
3 3 2 4 my_work_day_job_is2
4 2 3 3 my_work_day_job_is1
6 1 1 6 my_work_day_job_is0
7 5 5 3 my_work_day_job_is4
7 4 5 4 my_work_day_job_is3
10 10 10 6 my_work_day_job_is9
10 7 7 5 my_work_day_job_is6
10 6 5 4 my_work_day_job_is5

Next TopicName Mangling and Extern "C" in C++ Concept

← prev next →

For Videos Join Our Youtube Channel: Join Now

Feedback

Send your Feedback to [email protected]

Help Others, Please Share

Learn Latest Tutorials

Splunk

SPSS

Swagger

Transact-SQL

Tumblr

ReactJS

Regex

Reinforcement Learning

R Programming

RxJS

React Native

Python Design Patterns

Python Pillow

Python Turtle

Keras

Preparation

Aptitude

Reasoning

Verbal Ability

Interview Questions

Company Questions

Trending Technologies

Artificial Intelligence

AWS

Selenium

Cloud Computing

Hadoop

ReactJS

Data Science

Angular 7

Blockchain

Git

Machine Learning

DevOps

B.Tech / MCA

DBMS

Data Structures

DAA

Operating System

Computer Network

Compiler Design

Computer Organization

Discrete Mathematics

Ethical Hacking

Computer Graphics

Software Engineering

Web Technology

Cyber Security

Automata

C Programming

C++

Java

.Net

Python

Programs

Control System

Data Mining

Data Warehouse

Javatpoint Services

JavaTpoint offers too many high quality services. Mail us on h[email protected], to get more information about given services.

Website Designing
Website Development
Java Development
PHP Development
WordPress
Graphic Designing
Logo
Digital Marketing
On Page and Off Page SEO
PPC
Content Development
Corporate Training
Classroom and Online Training
Data Entry

Training For College Campus

JavaTpoint offers college campus training on Core Java, Advance Java, .Net, Android, Hadoop, PHP, Web Technology and Python. Please mail your requirement at [email protected].
Duration: 1 week to 2 week

^{Like/Subscribe us for latest updates or newsletter}

C++ Tutorial

C++ Control Statement

C++ Functions

C++ Arrays

C++ Pointers

C++ Object Class

C++ Inheritance

C++ Polymorphism

C++ Abstraction

C++ Namespaces

C++ Strings

C++ Exceptions

C++ Templates

Signal Handling

C++ File & Stream

C++ Misc

C++ STL Tutorial

C++ Iterators

C++ Programs

MCQ

Interview Question

Multiple Comparisons in a C++ Priority Queue

C++ Code

C++ Code

Feedback

Help Others, Please Share

Learn Latest Tutorials

Preparation

Trending Technologies

B.Tech / MCA

Javatpoint Services

Training For College Campus