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Question

I am having some difficulties in finishing this piece of code. Basically, I have to count the amount of times a letter should appear in a given string. For example, ABA should output the following

"A appears 1 times"
"B Appears 1 times"
"A Appears 1 times"

However the following code that I wrote does the following (It is part of a method)

public static char[] counter(char[] original, char[] manipulated) {
    int counter =0;
        for (int i=0; i<manipulated.length; i++) {
            for (int j=0; j<original.length; j++) {
                if (original[j] == manipulated[i]) {
                    counter++;
                } else {
                    
                }
            }
            System.out.println(manipulated[i] + " appears " + counter + " times");
            counter = 0;
        }
    
    return manipulated;
}

The output is this:

"A appears 2 times"
"B appears 1 times"
"A appears 2 times"

Which is not wrong, but that is not how I want it. So could you please assist me on this as soon as possible. I know that I am suppose to reset some variable but I am not sure where to actually reset it.

*Some notes: The variable manipulated is just the string that contains no duplicates so original would be abaa and manipulated would be aba :)

Answer 1

If your expected behaviour is just "print out the number of times each character appears in a row" then I am not sure why you need the manipulated variable at all. Your current code just accepts it as an argument and then returns it unchanged.

So unless I am misunderstanding the problem it could be a much simpler matter of:

void showConsecutiveCharacterCounts(char[] input) {
    int consecutiveCount = 0;
    /* iterate through all chars */
    for (int i = 0; i < input.length; i++) {
        /* increment count - will be 1 first time */
        consecutiveCount++;
        /* if we are at the end of a sequence of chars
           I.e. end of input OR next char does not match */
        if (i == input.length - 1 || input[i] != input[i + 1]) {
            /* print previous sequence */
            System.out.println(input[i] + " appears " + consecutiveCount + " times");
            /* and reset count */
            consecutiveCount = 0;
        }
    }
}

Answer 2

If you want to know how many times the same character appear in a row, you could change your code to

  public static void main(String[] args) {
    System.out.println(counter("AAACCAAAAAAAB"));
  }

  public static String counter(String s) {
    int counter = 0;
    int j;
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < s.length(); ) {
      j = i;
      char c = s.charAt(i);
      for (; j < s.length(); j++) {
        if (counter == 0) {
          sb.append(c);
        }
        if (c == s.charAt(j)) {
          counter++;
        } else {
          break;
        }
      }
      System.out.println(s.charAt(i) + " appears " + counter + " times");
      counter = 0;
      i = j;
    }
    return sb.toString();
  }

UPDATE changed the code so that you do not need to provide two char[] - now you input any String like "AAACCAAAAAAAB" (aka 'original') and the char[] formerly known as 'manipulated' will be returned by the method.

Result: A appears 3 times C appears 2 times A appears 7 times B appears 1 times ACAB