Java: substitution in a string according to several rules

Question

I have the following task. There is a line. I have to make a replacement in it in accordance with 6 rules until you can make a replacement in the line.

The solution I found is given below. It is working correctly. The problem is that its performance is low. How else can I make a replacement according to several rules? Is there any algorithm?

PS This task is related to the site of vulnerability. I got 100% correctness and 25% performance for my solution.

class Test {

    private Map<String,String> rules;

    private void initRules(){
        rules=new HashMap<>();
        rules.put("AB", "AA");
        rules.put("BA", "AA");
        rules.put("CB", "CC");
        rules.put("BC", "CC");
        rules.put("AA", "A");
        rules.put("CC", "C");
    }

    public String test(String S) {
        initRules();
        loop:while(true){
            String oldString=S;
            for (Map.Entry<String, String> rule : rules.entrySet())
            {
                S=S.replace(rule.getKey(), rule.getValue());
            }
            if (oldString==S){
                break loop;
            };
        }
        return S;
    }
}

 public class NewMain {

    public static void main(String[] args) {
        Test test=new Test();
        System.out.println("Result:"+test.test("ABBCC"));;
    }

}

Answer 1

Here is an algorithm you can use:

Assumption: The string consists only of (A, B, C)

B's ( A/C), output = .

:

. (B, A) (B, C), . A C. .

. : "BBBAABABBBCCBCBBCACB". :

"BBBAABABBB" "CCBCBBC" "A" "CB"

: ACAC

, B's A's A C's C.

Answer 2

. . AB → AA, AA → A, AB- > A

public static String stringReduce(String s){
  String transformed = s.replace("AA", "A").replace("CC", "C")
   .replace("BC", "C").replace("CB", "C").replace("BA", "A")
   .replace("AB", "A");

  if(transformed.equals(s)){
    return transformed;
  }
  else{
    return stringReduce(transformed);
  }
}

Answer 3

while :

:

public String stringReduce(String input) {
    String previous;
    do {
        previous = input;
        input = input.replace("AA", "A").replace("CC", "C").replace("BC", "C").replace("CB", "C")
                .replace("BA", "A").replace("AB", "A");
    } while (!previous.equals(input));
    return input;
}

Answer 4

python .

: "ABACAABBCA".

: AB → A, AA- > A, BC- > C. strng - "AACACA"

-, : AA- > A. strng - "ACACA"

, : , (strng). , - .

def solution(strng):
  prevS=""
  subst={"AB":"A","BA":"A","CB":"C","BC":"C","AA":"A","CC":"C"}
  subs=lambda st:subst[st.group(0)]
  while prevS!=strng:
      prevS=strng
      strng=re.sub(r'(([A][BA])|([B][A])|([CB][C])|([C][B]))',subs,strng)
  return strng

Answer 5

@vish4071.

"B" "A" , , "A" . "B" "C" .

"BAABBABAB" "A" - replace("AB" by "AA"),replace("BA" by "AA"), replace("AA" by "A")

: "BBBAABABBBCCBCBBCACB"

"BBBAABABBB" "CCBCBBC" "A" "CB"

"A" "C" "A" "C"

: "ACAC"

, "A" / "C" . char. "A" "C" "C" "A" , char . char.

: O (n)

: O (1)

Java.

  public static String solution(String S) {

        final char C = 'C';
        final char A = 'A';

        // if contains only B return itself
        if(!S.contains("A") || !S.contains("C")) return S;

    String res = "";
    boolean hasLetterChanged = false;
    char prevChar = 'D';
    for(char c : S.toCharArray()){
        if (c == A){
            if (prevChar == C){hasLetterChanged = true;}
        }else if(c == C){
            if (prevChar == A){hasLetterChanged = true;}
        }
        if(hasLetterChanged){
            res = res + prevChar;
            hasLetterChanged = false;
        }
        if(c == A || c == C){
            prevChar = c;
        }
    }

    return res + prevChar;
}

Python 2.7 ( 3x).

def solution(S):
    if not(S.__contains__('C') and S.__contains__('A')): return S

    has_char_changed = False
    prev_char = 'B'
    A = 'A'
    C = 'C'
    res = ""
    for c in S:
        if c == A:
            if prev_char == C:
                has_char_changed = True
        elif c == C:
            if prev_char == A:
                has_char_changed = True

        if has_char_changed:
            res = res + prev_char
            has_char_changed = False

        if c == A or c == C:
            prev_char = c

    return res + prev_char


if __name__ == '__main__':
    assert solution("ABBCC") == "AC"
    assert solution("BCBCABB") == "CA"
    assert solution("BBBAABABBBCCBCBBCACB") == "ACAC"
    assert solution("BBBBBBB") == "BBBBBBB"

Answer 6

#:

public static string solution(string S)
    {
        return Getreplace(S);
    }

    public static string Getreplace(string input)
    {
        string retval = input.Replace("AB", "AA")
                    .Replace("BA", "AA")
                    .Replace("CB", "CC")
                    .Replace("BC", "CC")
                    .Replace("AA", "A")
                    .Replace("CC", "C");

        if (input == retval)
            return retval;
        else
            return Getreplace(retval);
    }