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Security Code Validation

ISC 2006 Computer Science Practical, Question 3 · Strings

The question

A new advanced Operating System, incorporating the latest hi-tech features has been designed by Opera Computer Systems.

The task of generating copy protection codes to prevent software piracy has been entrusted to the Security Department.

The Security Department has decided to have codes containing a jumbled combination of alternate uppercase letters of the alphabet starting from A upto K (namely among A,C,E,G,I,K).

The code may or may not be in the consecutive series of alphabets.

Each code should not exceed 6 characters and there should be no repetition of characters. If it exceeds 6 characters, display an appropriate error message.

Write a program to input a code and its length. At the first instance of an error display invalid!” stating the appropriate reason. In case of no error, display the message “Valid!”.

Test your program for the following data and some random data.

SAMPLE DATA
INPUT:  N = 4
ABCE
OUTPUT:
Invalid! Only alternate letters permitted!

INPUT:  N = 4
AcIK
OUTPUT:
Invalid! Only upper case letters permitted!

INPUT:  N = 4
AAKE
OUTPUT:
Invalid! Repetition of characters not permitted!

INPUT:  N = 7
OUTPUT:
Error! Length of string should not exceed 6 characters!

INPUT:  N = 4
AEGIK
OUTPUT:
Invalid! String length not the same as specified!

INPUT:  N = 3
ACE
OUTPUT:
Valid!

INPUT:  N = 5
GEAIK
OUTPUT:
Valid!

Question: ISC 2006 Computer Science Paper 2 (Practical), Question 3, set by the Council for the Indian School Certificate Examinations (CISCE). Solution and video: Vinay Singh.

Java solution

ISC2006Q3.java Download GitHub

import java.util.*;

class CopyProtectionCode {
    private String code, output;
    private static String validCharacters = "ACEGIKacegik";
    private int N;

    public CopyProtectionCode(String code, int N) {
        this.code = code;
        this.N = N;
        validate();
    }

    private void validate() {
        if (N != code.length()) {
            output = "Invalid! String length not the same as specified!";
            return;
        }
        char ch;
        int foundAtPosition;
        for (int position = 0; position < code.length(); position++) {
            ch = code.charAt(position);
            foundAtPosition = validCharacters.indexOf(ch);
            if (foundAtPosition == -1) {
                output = "Invalid! Only alternate letters permitted!";
                return;
            }
            if (foundAtPosition > 5) {
                output = "Invalid! Only upper case letters permitted!";
                return;
            }
            if(code.lastIndexOf(ch)!=position){
                output="Invalid! Repetition of characters not permitted!";
                return;
            }
            output="Valid!";
        }
    }
    public String toString(){
        return output;
    }
}

public class ISC2006Q3 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("INPUT:\t");
        int N = in.nextInt();
        in.nextLine();
        if (N > 6) {
            System.out.println("OUTPUT:\nError! Length of string should not exceed 6 characters!");
        }else{
            String code = in.nextLine();
            CopyProtectionCode obj = new CopyProtectionCode(code, N);
            System.out.println("OUTPUT:\n" + obj);
        }
        

        in.close();
    }
}

Security Code Validation

The question

Java solution

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