HackerRank Java Priority Queue problem solution

HackerRank Java Priority Queue problem solution – In this HackerRank Java Priority Queue problem in the java programming language you need to Create the following two classes:

The Student class should implement:

• The constructor Student(int id, String name, double cgpa).
• The method int getID() to return the id of the student.
• The method String getName() to return the name of the student.
• The method double getCGPA() to return the CGPA of the student.

The Priorities class should implement the method List<Student> getStudents(List<String> events) to process all the given events and return all the students yet to be served in the priority order.

HackerRank Java Priority Queue problem solution.

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
/*
 * Create the Student and Priorities classes here.
 */
 import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Scanner;

import java.util.*;
class Student implements Comparable<Student>{
    String name = new String();
    double cgpa;
    int id;
    public Student(String name,double cgpa,int id)
    {
        this.name = name;
        this.cgpa = cgpa;
        this.id = id;
    }
    public String getName(){
        return this.name;
    }
    public int compareTo(Student s)
    {
        if(cgpa == s.cgpa)
        {
            if(name.compareTo(s.name) == 0)
            {
                if(id == s.id)
                    return 0;
                else if (id > s.id)
                    return 1;
                else
                    return -1;
            }
            else
                return name.compareTo(s.name);
        }
        else if(cgpa > s.cgpa)
            return -1;
        else
            return 1;
    }
}

class Priorities{
    public ArrayList<Student> getStudents(List<String> events)
    {
        int n = events.size();
        PriorityQueue<Student> pq = new PriorityQueue<Student>();
        for(String i:events)
        {
            String[] s = new String[4];
            s = i.split("\s");
            if(s.length>1)
            {
                pq.add(new Student(s[1],Double.valueOf(s[2]),Integer.valueOf(s[3])));
            }
            else
            {
                pq.poll();
            }
        }
        while(pq.size()>1)
        {
            System.out.println(pq.poll().name);
        }
        return new ArrayList<Student>(pq);
    }
}


public class Solution {
    private final static Scanner scan = new Scanner(System.in);
    private final static Priorities priorities = new Priorities();
    
    public static void main(String[] args) {
        int totalEvents = Integer.parseInt(scan.nextLine());    
        List<String> events = new ArrayList<>();
        
        while (totalEvents-- != 0) {
            String event = scan.nextLine();
            events.add(event);
        }
        
        List<Student> students = priorities.getStudents(events);
        
        if (students.isEmpty()) {
            System.out.println("EMPTY");
        } else {
            for (Student st: students) {
                System.out.println(st.getName());
            }
        }
    }
}

Second solution

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

class Student{
    private int token;
    private String fname;
    private double cgpa;
    public Student(int id, String fname, double cgpa) {
        super();
        this.token = id;
        this.fname = fname;
        this.cgpa = cgpa;
    }
    public int getToken() {
        return token;
    }
    public String getFname() {
        return fname;
    }
    public double getCgpa() {
        return cgpa;
    }
}

class StudentComparator implements Comparator<Student> {
    public int compare(Student s1, Student s2) {
        if (s1.getCgpa() > s2.getCgpa()) {
            return -1;
        }
        if (s1.getCgpa() < s2.getCgpa()) {
            return 1;
        }
        if (s1.getFname().compareTo(s2.getFname()) < 0) {
            return -1;
        }
        if (s1.getFname().compareTo(s2.getFname()) > 0) {
            return 1;
        }
        if (s1.getToken() < s2.getToken()) {
            return -1;
        }
        if (s1.getToken() > s2.getToken()) {
            return 1;
        }
        return 0;
    }
}

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int totalEvents = Integer.parseInt(in.nextLine());
        PriorityQueue<Student> pq = new PriorityQueue(totalEvents, new StudentComparator());
            while(totalEvents>0){
            String event = in.next();
            if (event.equals("ENTER")) {
                String fname = in.next();
                double cgpa = in.nextDouble();
                int id = in.nextInt();
                Student s = new Student(id, fname, cgpa);
                pq.add(s);
            }
            else {
                pq.poll();
            }

            totalEvents--;
        }
        if (pq.isEmpty()) {
            System.out.println("EMPTY");
        }
        while (!pq.isEmpty()) {
            System.out.println(pq.poll().getFname());
        }
    }
}

The solution in java programming

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

class Student{
   private int token;
   private String fname;
   private double cgpa;
   public Student(int id, String fname, double cgpa) {
      super();
      this.token = id;
      this.fname = fname;
      this.cgpa = cgpa;
   }
   public int getToken() {
      return token;
   }
   public String getFname() {
      return fname;
   }
   public double getCgpa() {
      return cgpa;
   }
}

public class Solution {

  public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int totalEvents = Integer.parseInt(in.nextLine());
        PriorityQueue<Student> list =
                new PriorityQueue<>(new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                if(o1.getCgpa() != o2.getCgpa())
                    return o1.getCgpa() < o2.getCgpa() ? 1 : -1;
                else{
                    if(!o1.getFname().equals(o2.getFname()))
                        return o1.getFname().compareTo(o2.getFname());
                    else
                        return o1.getToken() < o2.getToken() ? 1 : -1;
                }
            }
        });

        while(totalEvents>0){
            String event = in.next();

            if(event.equals("ENTER")){
                String name = in.next();
                double gpa = in.nextDouble();
                int id = in.nextInt();
                list.add(new Student(id, name, gpa));
            }else if(list.size() > 0 && event.equals("SERVED")){
                list.remove();
            }

            totalEvents--;
        }

        if(list.size() == 0) {
            System.out.println("EMPTY");
            return;
        }

        while(list.size() > 0){
            System.out.println(list.poll().getFname());
        }
    }
}