P2 - 2021/22 - DN06 - Starc Aljaz

class DN06 {
    public static void main (String[] args) {
        String str = "";
        for (int i=0;i<args[0].length();i++) str += "a";

        while (true) {
            if (bsdChecksum(str) == bsdChecksum(args[0])) {
                System.out.println(str);
                break;
            } else {
                str = flip(str);
            }
        }
    }

    static String flip (String niz) {
        int index = niz.length() - 1;
        while (index + 1 >= 0) {
            int cAscii = (int) niz.charAt(index);
            if (cAscii == 122) {
                niz = niz.substring(0, index) + "a" + niz.substring(index + 1);
                index -= 1;
            } else {
                int nAscii = cAscii + 1;
                return niz.substring(0, index) + ((char) nAscii) + niz.substring(index + 1);
            }
        }
        return niz;
    }

    static int bsdChecksum (String niz) {
        // https://en.wikipedia.org/wiki/BSD_checksum
        int checksum = 0;

        for (int i = 0; i<niz.length(); i++) {
            checksum = (checksum >> 1) + ((checksum & 1) << 15);
            checksum += niz.charAt(i);
            checksum &= 0xffff;       
        }
        return checksum;
    }
}

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Zadnja posodobitev: April 5, 2022