CODEWITHSUNDEEP
java
Suraj Palwe
Suraj Palwe

Reputation: 2120

Why boolean value is not changing?

I am learning java step by step:

I have a practice problem problem statement link and this is my code:

import java.util.Scanner;

public class Solution {

public static void main(String[] args) {
    int test, numProcess = 0;
    boolean checkString ;
    String alpha = "abcdefghijklmnopqrstuvwxyz";
    Scanner sc = new Scanner(System.in);
    test = sc.nextInt();
    for (int i = 0; i < test; i++) {
        String original = sc.nextLine();
        checkString = checkPalindrome(original);
        while (!checkString) {
            char oldchar = original.charAt((original.length() - 1));
            char newchar = alpha.charAt((original.indexOf(oldchar) - 2));
            original = original.substring(0, original.length()-1)+ newchar;
            checkString = checkPalindrome(original);
            numProcess++;
        }
        System.out.println(numProcess);
    }

    sc.close();
}

public static boolean checkPalindrome(String original) {
    String newString = "";
    for (int i = (original.length() - 1); i >= 0; i--) {
        newString += original.charAt(i);
    }
    return (newString.equals(original));
 }
}

the problem is when we try as input,

  1. "abc" as string(IN WHILE LOOP) 1st iteration makes original = abb then goes to function which returns false(that is right)
  2. in 2nd iteration original = aba which should return checkString = true;
  3. and next time while loop should be bypassed but it again enters into while loop (I tried this in debugger)and makes throws exception at line containing newchar(Index out of bounds) what is the problem ??

Upvotes: 0

Views: 125

Answers (3)

Suraj Palwe
Suraj Palwe

Reputation: 2120

I have figured out what was the real problem .. when reading string through scanner like as an example in the format testcase(how many int) and string(check for this string solution) -> 1 abc .. the string will be readed as " abc" and not "abc" which is the error i made in accepting string as input by making sc.nextLine(); which should be used as sc.next(); so checkPalindrome was always returning false ... hushhhhh!!! at last got the solution..

Vote up if I am right

Upvotes: 0

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35557

First of all, If you put input as abc. Your code will throws an Exception

Scanner sc = new Scanner(System.in);
test = sc.nextInt(); // reading an int

While you are putting abc.

You are trying to find whether given String is palindrome, You can do it as following way easily.

public static boolean isPalindrome(String original) {
    StringBuilder sbOriginal = new StringBuilder();
    sbOriginal.append(original);
    StringBuilder sbReverse=sbOriginal.reverse();
    return  sbOriginal.toString().equals(sbReverse.toString());
}

Run This code.

Upvotes: 1

TEXHIK
TEXHIK

Reputation: 1398

 for (int i = (original.length() - 1); i > 0; i--)

Your new string doesn't contains first character: the "abc" string will become to "cb". You should change your for condition to i >= 0 or i > -1

Upvotes: 0

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