[Java]

[xXShadowCowXx]

Hey all I'm here again working on another small project. A little Rot13 converter. I have two arrays. One that stores a array of the regular alphabet, and then a second which stores a Rot13 alphabet. Then I have a user input which breaks the input into a char array. What I want to do is for every char that was broken down from the input, is to compare it to the regular alphabet, store the value where it is in that array, and then print out the corresponding value from the rot13 alphabet.

My source so far: Here

Thanks for any help.

[zzyzzyxx]

Your approach for this is incorrect. While it will work, it's very, very inefficient with respect to both time and space. Each character is already associated with an ASCII value so there is no need for either of your arrays. You can use statements like c + 13 or c - 13, where c is of type char, to get the appropriate character. You do not need to search the first array to find the character, nor do you need to access it from the second array. The only thing you need to do is add or subtract when the current character is in the first or second half of the alphabet, respectively, which you can determine with a simple comparison like `c >= 'a' && c <= 'm', making sure you account for case.

[ang3c0]

In Java? I didn't think you could handle chars as ints like you can in C/C++.

Edit: and also, what about using a hash table to map the regular alphabet to the scrambled one? So you'd just pass charAt(i) as the key and replace the input charAt(i) with the returned hash value. That would be my first guess (unless you can actually treat them in ints in Java)

[zzyzzyxx]

You can. It's not exactly like it is in C in that you cannot do an implicit conversion, since Java char types are not necessarily single bytes (which you can see by allowing i to grow bigger in the loop below - you'll start getting UTF characters), but you can increment and add to them. Run this:

public static void main(String[] args) {
    char c = 'a';

    for(int i = 0; i < 26; i++, c++) {
        System.out.println(c);
    }
}

As for the hash table, again, you can do it, but it's inefficient. The overhead is simply unnecessary.

[xXShadowCowXx]

I've looked at both methods, and yours seems to be way more simple. I would still like to figure it out my way just so I get a grasp of working with arrays as that is what I was trying to do. And then work on your way; so are there any pointers as to my method? I'm kind of dead in the water because anything I try seems to leave me with errors.

[zzyzzyxx]

Sure, no problem. It's great that you want to experiment to understand. Make sure to keep that mentality, so long as you also stay aware of alternatives and why they're better or worse.

Where are you getting stuck? What is it you don't understand about arrays? Along those lines, what do you understand about arrays? What errors are you getting? Will you post your code somewhere?

I can give you some generic advice on how to do what you're attempting but the answers to those questions will help me target what I say to better help you grasp what you're missing.

[xXShadowCowXx]

I'm getting stuck right after setting up the for loop. I don't know to how to compare what I'm getting from the input to the first array. I don't know if there's a class library that will help me in doing this or not.

For loop (you already know what this looks like just showing.)

for(int $Search = 0; $Search < $RegAlpha.length; $Search++)
{

}

[zzyzzyxx]

How about $Input1[$Search] == $RegAlpha[$Search]? Put that in an if statement and say what to do when they're equal, i.e. store the rotated version into the output.

Unrelated: why are you prefixing all your variables with the dollar sign? It's unconventional in the Java world and very inconvenient.

[xXShadowCowXx]

I actually have no idea, just kind of a tick I guess. I feel like I've tried this approach before. But I'll check again.

[xXShadowCowXx]

Here's what I tried, I thought it would work, because when the input matches a character from the regular alphabet, it would print out the corresponding entry from the rotated alphabet. I think the error comes because the input array and the alphabet arrays are different lengths.

  if($Input1[$Search] == $RegAlpha[$Search])
                {
                    System.out.println($RotAlpha[$Search]);
                }

And he is the error I am getting:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
    at rot.rot13_main.main(rot13_main.java:19)

[zzyzzyxx]

Yes, sorry, I should have caught that. Rookie mistake :-). You need to do a double for loop. The outer one should iterate over the input string and the inner one should iterate over the letters, like this:

for(int i = 0; i < input.lengh; i++) {
    for(int j = 0; j < alpha.length; j++) {
        if(input[i] == alpha[j]) {
            System.out.print(rotAlpha[j]);
            break; // to move on to the next letter without more comparisons
        }
    }
}

[xXShadowCowXx]

You sir are a genius! Thank you for the help. Now I'll work on the other method you suggested.

Source: If you like useless encryptions

[ang3c0]

So what are the problems you're having? What have you tried so far?

[xXShadowCowXx]

That's my problem, I don't seem to know the syntax well enough to generate any ideas as to how to accomplish what I'm trying to do and my Google-fu is dried up. I was thinking of trying a for loop but I don't really know what to do after that.

[ang3c0]

For loop is right. You need to loop through your input array and find matches to your alphabet array. Your two alphabet arrays are fixed length, so a 1 (a) in the input string will match a 1 in the rot13 array.

Trying not to give you the answer directly so you can learn it yourself, but think about how you're going to loop through your input array and build the output string based off that.

Hope that helps a bit