Day 12: HackerRank 30 Days Of Code Solution | Inheritance

This post explains the HackerRank 30 Days of Code problem Inheritance step by step: the problem statement, input and output format, constraints, a sample test case and a working solution in Java that you can study and run.

Day 12: Inheritance

Objective

Here we are dealing with Inheritance. So Codinghumans lets know what is inheritance.
Inheritance in java allows to build new classes from existing classes and make s resuse of codes easier.

Mission

Given two classes, Person and Student, where Person is the base class and Student is the derived class. Completed code for Person and a declaration for Student are provided for you in the editor. Observe that Student inherits all the properties of Person.

Complete the Student class by writing the following:
A Student class constructor, which has 4 parameters:
a. A string, firstName.

b. A string, lastName .
c. An integer, id.
d. An integer array (or vector) of test scores, .

A char calculate() method that calculates a Student object's average and returns the grade character representative of their calculated average:

how score is grades ,For Average a

Inheritance Solution

if 90<=a<=100        grade is O
else if 90<=a<=100 grade is E
else if 90<=a<=100 grade is A
else if 90<=a<=100 grade is P
else if 90<=a<=100 grade is D
else if 90<=a<=100 grade is T

Input Format

The locked stub code in your editor calls your Student class constructor and passes it the necessary arguments. It also calls the calculate method (which takes no arguments).

The first line contains , firstName, lastName and id , respectively. The second line contains the number of test scores. The third line of space-separated integers describes .

Constraints

1<=|FirstName|,|lastName|<=10
|id|= =7
0<= score,average<=100

Output Format

This is handled by the locked stub code in your editor. Your output will be correct if your Student class constructor and calculate() method are properly implemented.

Sample Input

Sans Sherpa 425698
2
70 90

Sample Output

Name: Sherpa, Sans
ID: 425698
Grade: E

Explanation

This student had 2 scores to average:70 and 90. The student's average grade is 80 . An average grade of corresponds to the letter grade , so our calculate() method should return the character'E'.

Inheritance Solution in Java

import java.util.*;
class Person {
 protected String firstName;
 protected String lastName;
 protected int idNumber;
 
 // Constructor
 Person(String firstName, String lastName, int identification){
  this.firstName = firstName;
  this.lastName = lastName;
  this.idNumber = identification;
 }
 
 // Print person data
 public void printPerson(){
   System.out.println(
    "Name: " + lastName + ", " + firstName 
   +  "\nID: " + idNumber); 
 }
  
}

class Student extends Person{
 private int[] testScores;
    public Student(String firstName,String lastName,int id,int []testScores){
        super(firstName,lastName,id);
        this.testScores=testScores;
        this.firstName = firstName;
        this.lastName = lastName;
        this.idNumber = id;
    }
        public char calculate(){
            int sum= 0; 
            int a=0;
            for(int i=0;i<testScores.length;i++){
                a=a+testScores[i];
            }
            a=a/testScores.length;
            if(90<=a&&a<=100){
                return 'O';
            }else if(80<=a&&a<90){
                return 'E';
            }else if(70<=a&&a<80){
                return 'A';
            }else if(55<=a&&a<70){
                return 'P';
            }else if(40<=a&&a<55){
                return 'D';
            }else if(0<=a&&a<40){
                return 'T';
            }
            else
            return Character.MIN_VALUE;
        }
    
}

class Solution {
 public static void main(String[] args) {
  Scanner scan = new Scanner(System.in);
  String firstName = scan.next();
  String lastName = scan.next();
  int id = scan.nextInt();
  int numScores = scan.nextInt();
  int[] testScores = new int[numScores];
  for(int i = 0; i < numScores; i++){
   testScores[i] = scan.nextInt();
  }
  scan.close();
  
  Student s = new Student(firstName, lastName, id, testScores);
  s.printPerson();
  System.out.println("Grade: " + s.calculate());
 }
}

If you need solutions in other programming languages or have any doubts regarding this problem then leave a comment down below .

Tip: try to solve the problem yourself before reading the solution. Use the code as a reference to check your approach, and make sure you understand why it works.

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