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  1. Prepare
  2. Java
  3. Data Structures
  4. Java Priority Queue
  5. Discussions

Java Priority Queue

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271 Discussions

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  • nguyenvoleduong1
     + 0 comments

    `class Student{ private int id; private String name; private 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 getStudents(List events){ PriorityQueue queue = new PriorityQueue<>( new Comparator() { public int compare(Student stu1, Student stu2){ if(stu1.getCGPA()!= stu2.getCGPA()){ return Double.compare(stu2.getCGPA(), stu1.getCGPA()); }else if (!stu1.getName().equals(stu2.getName())){ return stu1.getName().compareTo(stu2.getName()); }else { return stu1.getID() - stu2.getID(); } } } );

        for (String e : events){
        String[] part = e.split(" ");
        if(part[0].equals("ENTER")){
            String name = part[1];
            double cgpa = Double.parseDouble(part[2]);
            int id = Integer.parseInt(part[3]);
            queue.add(new Student(id, name, cgpa));
        }else if (part[0].equals("SERVED")){
            queue.poll();
        }
    }

    List<Student> result = new ArrayList<>();
    while (!queue.isEmpty()){
        result.add(queue.poll());
    }
    return result;
}

    }`

    `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 input = new Scanner(System.in);
    int n = Integer.parseInt(input.nextLine());

    List<String> events = new ArrayList<>();
    while (n-- > 0){
        events.add(input.nextLine());
    }

    Priorities priorities = new Priorities();
    List<Student> students = priorities.getStudents(events);

    if(students.isEmpty()){
        System.out.println("EMPTY");
    }else {
        for (Student s : students){
            System.out.println(s.getName());
        }
    }
}

    }`

  • ZollerObrien
     + 0 comments

    PriorityQueue is excellent when you need a dynamically sized structure that retrieves elements based on priority efficiently. But for use cases needing sorted iteration or random access, alternatives like TreeSet or ArrayList + sorting should be considered. 11xplay ID

  • danielamedeirom1
     + 0 comments

    public class Solution {

    private final static Scanner sc = new Scanner(System.in);
private final static Priorities priorities = new Priorities();

public static void main(String[] args) {

   int totalEventos = Integer.parseInt(sc.nextLine().trim());
   List<String> events = new ArrayList<>();

   for (int i=0; i < totalEventos; i++){
    events.add(sc.nextLine().trim());
   }

    List<Student> students = priorities.getStudents(events);

    if (students.isEmpty()) {
            System.out.println("EMPTY");
    } else {
        for (Student s : students) {
            System.out.println(s.getName());
        }
    }
   sc.close();
}

static class Student {
    private int id;
    private String name;
    private 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;
    }
}

static class Priorities {

    public List<Student> getStudents(List<String> events){
        PriorityQueue<Student> fila = new PriorityQueue<>(
                Comparator.comparing(Student::getCGPA).reversed()
                .thenComparing(Student::getName)
                .thenComparing(Student::getID)
        );

        for(String enter : events) {
            String[] result = enter.split(" ");

            if(result[0].equalsIgnoreCase("ENTER")){
                    fila.add(new Student(Integer.parseInt(result[3]), 
                    result[1], 
                    Double.parseDouble(result[2])
                    ));
            } else if (result[0].equals("SERVED")) {
                    fila.poll();
            }
        }

        List<Student> restantes = new ArrayList<>();
        while(!fila.isEmpty()) {
                restantes.add(fila.poll());
        }
        return restantes;
    }

}

    }

  • Damian_GDO_92
     + 0 comments
    import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.PriorityQueue;

class Student implements Comparable<Student> {
    private int id;
    private String name;
    private 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;
    }
    
    public int compareTo(Student cStudent) {
        if (cgpa != cStudent.getCGPA()) {
            return Double.compare(cStudent.getCGPA(), cgpa);
        } else if (!name.equals(cStudent.getName())) {
            return name.compareTo(cStudent.getName());
        } else {
            return Integer.compare(id, cStudent.getId());
        }
    }
}

class Priorities {
    public List<Student> getStudents(List<String> events) {
        
        List<Student> servedStudents = new ArrayList<>();
        PriorityQueue<Student> queue = new PriorityQueue<Student>();

        for (String event : events) {
            String[] parsedEvent = event.split("\\s+");
            
            if ("ENTER".equals(parsedEvent[0])) {
                Student student = new Student(
                    Integer.parseInt(parsedEvent[3]), parsedEvent[1], Double.parseDouble(parsedEvent[2]));
                queue.add(student);
            } else if ("SERVED".equals(parsedEvent[0])) {
                queue.poll();
            }
        }

        while (!queue.isEmpty()) {
            servedStudents.add(queue.poll());
        }

        return servedStudents;
    }
}

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());
            }
        }
    }
}

  • laucarrizo332
     + 1 comment
     class Student implements Comparable<Student> {
    
    private int id;
    private String name;
    private double cgpa;
    
    public Student (int id, String name, double cgpa){
        this.id = id;
        this.name = name;
        this.cgpa = cgpa;
    }
    
     public int getId() {
        return this.id;
     }
     public String getName() {
        return this.name;
     }
     public double getCGPA(){
        return this.cgpa;
     }
   @Override
    public int compareTo(Student other) {
    if (this.cgpa != other.cgpa) return Double.compare(other.cgpa, this.cgpa);
    int nameComp = this.name.compareTo(other.name);
    if (nameComp != 0) return nameComp;
    return this.id - other.id;
}
 }
 class Priorities {
    public List<Student> getStudents(List<String> events) {
        int idStudent = 0;
        PriorityQueue<Student> queue = new PriorityQueue<>();
        for (int i = 0; i < events.size(); i++) {
            if (events.get(i).startsWith("ENTER")) {
                String[] parts = events.get(i).split(" ");
                String name = parts[1];
                double cgpa = Double.parseDouble(parts[2]);
                idStudent++;
                Student student = new Student(idStudent, name, cgpa);
                queue.add(student);
            } else if (events.get(i).startsWith("SERVED")) {
                queue.poll(); 
            }
        }

      
        List<Student> result = new ArrayList<>();
        while (!queue.isEmpty()) {
            result.add(queue.poll());
        }
        return result;
    }
}