Discussion on Java Priority Queue Challenge

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6 days ago+ 0 comments

Java 15 solution

import java.io.*;
import java.util.*;

class Student{
    
     private int id;
     private String name;
     private double cgpa;
     
     Student(int id, String name, double cgpa){
        this.id = id;
        this.name = name;
        this.cgpa = cgpa;
     }
     
     int getID(){
        return this.id;
     }
     
     String getName(){
        return this.name;
     }
     
     double getCgpa(){
        return this.cgpa;
     }
}

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

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        sc.nextLine();
        PriorityQueue<Student> pq = new PriorityQueue<Student>(n+1, new StudentComparator());
                
        for(int i=0;i<n;i++){
            String str = sc.nextLine();
            String operation = str.split(" ")[0];
            if(operation.equals("ENTER")){
                String name = str.split(" ")[1];
                double cgpa = Double.parseDouble(str.split(" ")[2]);
                int id = Integer.parseInt(str.split(" ")[3]);
                pq.add(new Student(id,name,cgpa));   
            }
            else if(operation.equals("SERVED")){
                pq.poll();
            }
        }
        
            List<Student> result = new ArrayList<>();
            while (!pq.isEmpty()) {
                result.add(pq.poll());
            }
                
            if (result.isEmpty()) {
                System.out.println("EMPTY");
            } else {
                    for (Student st: result) {
                            System.out.println(st.getName());
            }
            
        }

    }
}

2 weeks ago+ 0 comments

My solution with java 8

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
/*
 * Create the Student and Priorities classes here.
 */
import java.util.*;
class Student {
    public int id;
    public String name;
    public double cgpa;

    public Student(int id, String name, double cgpa){
        this.id = id;
        this.name = name;
        this.cgpa = cgpa;
    }

    public int getId(){ return id;}
    public String getName(){return name;}
    public double getCGPA(){return cgpa;}
}
class StudentComparator implements Comparator<Student>{

    @Override
    public int compare(Student s1, Student s2) {

        if(s1.cgpa == s2.cgpa){
            return s1.name.compareTo(s2.name);
        } else if (s1.cgpa == s2.cgpa && s1.name == s2.name){
            if(s1.id > s2.id)
                return 1;
            else
                return -1;
        } else if(s1.cgpa < s2.cgpa){
            return 1;
        } else if(s1.cgpa > s2.cgpa){
            return -1;
        } else {
            return 0;
        }
    }
}
class Priorities{
    public PriorityQueue<Student> q = new PriorityQueue<>(new StudentComparator());
    List<Student> student2List = new ArrayList<>();

    public List<Student> getStudents(List<String> events){
        for(String st : events){

            String[] parts = st.split(" ");

            if(parts[0].equals("ENTER")) {
                q.add(new Student(Integer.parseInt(parts[3]), parts[1], Double.parseDouble(parts[2])));

            } else if (parts[0].equals("SERVED")){
                q.poll();
            }
        }

        while(!q.isEmpty()){
            student2List.add(q.poll());
        }

        return student2List;
    }
}


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());
            }
        }
    }
}

2 months ago+ 0 comments

using a linked list for the queue

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.Collections;
import java.util.LinkedList;
import java.util.Comparator;

class Student{
    int id;
    String name;
    double cgpa;
    
    public Student(int id, String name, double cgpa){
        this.id = id;
        this.name = name;
        this.cgpa = cgpa;
    }
    public int getID(){
        return id;
    }
    public String getName(){
        return name;
    }
    public double getCGPA(){
        return cgpa;
    }
}

class Priorities{
    public List<Student> getStudents(List<String> events){
        LinkedList<Student> pq = new LinkedList<Student>(); 
  
        for(int i=0;i<events.size();i++){
            String[] entry = events.get(i).split("\\s+");
            
            if(entry[0].equals("ENTER")){

                Student s = new Student(Integer.parseInt(entry[3]), entry[1], Double.parseDouble(entry[2]));
                pq.add(s);
                
                
            }
            
            else if(entry[0].equals("SERVED")){
                //sort the queue first
                Collections.sort(pq, new CompareStudents());
                try{pq.removeFirst();}catch(Exception e){};
            }
        }
        return pq;
    }
}

class CompareStudents implements Comparator<Student>{
    public int compare(Student s1, Student s2){
        //sorting logic
        if(s1.cgpa<s2.cgpa){
            return 1;
        }
        if(s1.cgpa>s2.cgpa){
            return -1;
        }
        if(s1.name.compareTo(s2.name)!=0){
            return s1.name.compareTo(s2.name);
        }
       
        if(s1.id<s2.id){
            return -1;
        }
        if(s1.id>s2.id){
            return 1;
        }
        return 0;
    }
}




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());
            }
        }
    }
}

3 months ago+ 0 comments

import java[dot]util[dot]PriorityQueue ;
import java[dot]util[dot]LinkedList ;
class Student {
    private int id;
    private String name;
    private double cgpa;
    public Student(String name, double cgpa,int id) {
        this.id = id;
        this.name = name;
        this.cgpa = cgpa;
    }
    public int getID(){return id;}
    public String getName(){return name;}
    public double getCGPA(){return cgpa;}
};
class Priorities {
    private PriorityQueue<Student> queue;
    public Priorities() {
        queue = new PriorityQueue<>((s1, s2) -> {
            int[] res = {Double.compare(s2.getCGPA(),
            s1.getCGPA()),s1.getName().compareTo(s2.getName()),
            Integer.compare(s1.getID(), s2.getID())};
            for (int r : res){if (r != 0){return r;}}
            return 0;});
    }
    public List<Student> getStudents(List<String> events) {
        for (String event : events) {String[] e = event.split(" ");
            if (e[0].equals("ENTER")) 
            {queue.add(
                new Student(e[1], Double.parseDouble(e[2]),Integer.parseInt(e[3]))
                );}
            else if (e[0].equals("SERVED")) {queue.poll();}}
            LinkedList<Student> StudentsLeft = new LinkedList<>();
            while (!queue.isEmpty()) {StudentsLeft.add(queue.poll());}
            return StudentsLeft;}
}

3 months ago+ 0 comments

There might be more SERVED events than ENTER events, even though it's logically inconsistent.

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My solution with java 8

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