Question

i’m doing an encoding program where i’m supposed to delete every character in the string which appears twice. i’ve tried to traverse through the string but it hasn’t worked. does anyone know how to do this? Thanks.

public static String encodeScrambledAlphabet(String str)
{
    String newword = str;
    String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    newword += alphabet;

    newword = newword.toUpperCase();

    for (int i = 0, j = newword.length(); i < newword.length() && j >=0; i++,j--)
    {
        char one = newword.charAt(i);
        char two = newword.charAt(j);

        if (one == two)
        {
            newword = newword.replace(one, ' ');
        }



    }

    newword = newword.replaceAll(" ", "");

    return newword;
}

Answer 1

Assuming that you would like to keep only the first occurrence of the character, you can do this:

boolean seen[65536];
StringBuilder res = new StringBuilder();
str = str.toUpperCase();
for (char c : str.toCharArray()) {
    if (!seen[c]) res.append(c);
    seen[c] = true;
}
return res.toString();

The seen array contains flags, one per character, indicating that we’ve seen this character already. If your characters are all ASCII, you can shrink the seen array to 128.