public String doubleChar(String str) {
   String answerString = "";

   for (int i = 0; i < str.length(); i++) {
      String letter = str.substring(i,i+1);
      answerString += letter + letter;
   }

   return answerString;
}


public int countHi(String str) {
  int count = 0;

  for (int i = 0; i < str.length()-1; i++) {
    String s = str.substring(i, i+2);
    if (s.equals("hi")) {
      count ++;
    }
  }
  return count;
}


public boolean catDog(String str) {

  int dogCount = 0;
  int catCount = 0;

  for (int i = 0; i <= str.length()-3; i++) {
    if (str.substring(i,i+3).equals("dog"))
      dogCount++;
    else if (str.substring(i,i+3).equals("cat"))
      catCount++;
  }

  return (catCount == dogCount);
}


public int countCode(String str) {
  int count = 0;

  for (int i = 0; i <= str.length()-4; i++) {
    if (str.charAt(i)   == 'c' && str.charAt(i+1) == 'o' && str.charAt(i+3) == 'e') {
      count++;
    }
  }

  return count;
}


public boolean endOther(String a, String b) {
  String shorter = "";
  String longer  = "";

  if (a.length() <= b.length()) {
    shorter = a.toLowerCase();
    longer  = b.toLowerCase();
  } else {
    shorter = b.toLowerCase();
    longer  = a.toLowerCase();
  }

  String longerEnd = longer.substring(longer.length() - shorter.length());
  return longerEnd.equals(shorter);
}


public boolean xyzThere(String str) {

  if (str.length() < 3)  return false;
  if (str.length() == 3) return str.equals("xyz");
  if (str.substring(0,3).equals("xyz")) return true;

  for (int i = 1; i < str.length()-2; i++) {
    String xyzCandidate = str.substring(i,i+3);
    String before = str.substring(i-1,i);
    if (xyzCandidate.equals("xyz") && !before.equals("."))
      return true;
  }

  return false;
}


public boolean bobThere(String str) {
  for (int i = 0; i <= str.length()-3; i++) {
    if (str.charAt(i) == 'b' && str.charAt(i+2) == 'b') return true;
  }
  return false;
}


public boolean xyBalance(String str) {
  int lastX = str.lastIndexOf("x");
  int lastY = str.lastIndexOf("y");

  return (lastY > lastX || lastY == lastX);
}


public String mixString(String a, String b) {
  int maxlen = Math.max(a.length(), b.length());
  String ans = "";

  for (int i = 0; i < maxlen; i++) {
    String pieceOfA = "";
    String pieceOfB = "";
    if (i < a.length()) pieceOfA = a.substring(i,i+1);
    if (i < b.length()) pieceOfB = b.substring(i,i+1);
    ans += pieceOfA + pieceOfB;
  }

  return ans;
}


public String repeatEnd(String str, int n) {
  String end = str.substring(str.length()-n);
  String newString = "";

  for (int i = 0; i < n; i++) {
    newString += end;
  }

  return newString;
}


public String repeatFront(String str, int n) {
  String ans = "";

  for (int i = n; i > 0; i--) {
    ans += str.substring(0,i);
  }

  return ans;
}


public String repeatSeparator(String word, String sep, int count) {
  String ans = "";
  for (int i = 0; i < count; i++) {
    if (i == count-1) ans += word;
    else ans += word + sep;
  }
  return ans;
}


public boolean prefixAgain(String str, int n) {
  int strLen = str.length();
  String prefix = str.substring(0, n);

  for (int i = n; i <= strLen-n; i++) {
    String chunk = str.substring(i, i+n);
    if (chunk.equals(prefix)) return true;
  }

  return false;
}


public boolean xyzMiddle(String str) {

  if (str.length() < 3)  return false;
  if (str.length() == 3) return "xyz".equals(str);

  int midpoint = str.length() / 2;
  String oddCenter  = str.substring(midpoint-1, midpoint+2);
  String evenCenter = str.substring(midpoint-2, midpoint+1);

  if (str.length() % 2 == 1)
    return "xyz".equals(oddCenter);
  else
    return "xyz".equals(evenCenter) || "xyz".equals(oddCenter);
}


public String getSandwich(String str) {
  String answer = "";

  int b1 = str.indexOf("bread");
  int b2 = str.lastIndexOf("bread");
  if (b1 != b2) {
    answer = str.substring(b1+5, b2);
  }

  return answer;
}


public boolean sameStarChar (String str) {
  if (str.length() < 3) return true;

  for (int i = 1; i < str.length()-1; i++) {
    if (str.charAt(i) == '*') {
      char front = str.charAt(i-1);
      char back  = str.charAt(i+1);
      if (front != back)
        return false;
    }
  }

  return true;
}


public String oneTwo(String str) {
  String ans = "";

  while (str.length() >= 3) {
    String a  = str.substring(0,1);
    String bc = str.substring(1,3);
    ans += bc + a;
    str = str.substring(3);  //instead of moving the index forward, I cut away the front of str
  }

  return ans;
}


public String zipZap(String str) {

  //edge case: if the string is shorter than 3 chars, it can't contain zap
  if (str.length() < 3) return str;

  //Now parse through the string. I am using a while loop because I want to have
  //more control over the iteration step. Also, it is important to make sure
  //the variable i is available outside the loop for the last step.
  String ans = "";
  int i = 0;
  while ( i < str.length()-2) {
    if (str.charAt(i) == 'z' && str.charAt(i+2) == 'p') {
      ans += "zp";
      i += 3;
    } else {
      ans += str.charAt(i);
      i++;
    }
  }

  //add on the remaining letters, if necessary
  if (i < str.length()) {
    return ans + str.substring(i);
  } else {
    return ans;
  }

}


public String starOut(String str) {

  String answer = "";

  //deal with tiny strings
  if (str.length() < 3) {
    if (str.contains("*")) {
      return "";
    } else {
      return str;
    }
  }

  //process larger strings
  for (int i = 0; i < str.length()-1; i++) {
    String sub = str.substring(i,i+2);
    char a = str.charAt(i);
    char b = str.charAt(i+1);
    if (!sub.contains("*")) {
      answer += a;
    }
    else {
      if (a == '*' & b != '*') {
        i++; //skip ahead 2
      } else {
        //do nothing, will skip ahead 1 because of for loop
      }
    }
  }

  //deal with last character separately to avoid out of bounds
  String lastTwo = str.substring(str.length()-2);
  char lastChar = str.charAt(str.length()-1);
  if (!lastTwo.contains("*")) {
    answer += lastChar;
  }

  return answer;
}


public String plusOut(String str, String word) {
  String newString = "";
  int i = 0;
  int s = str.length();
  int w = word.length();

  while (i < s-w+1) {
    String chunk = str.substring(i, i+w);
    if (chunk.equals(word)) {
      newString += word;
      i += w;
    }
    else {
      newString += "+";
      i++;
    }
  }

  while (i < s) {
    newString += "+";
    i++;
  }

  return newString;
}


public String wordEnds(String str, String word) {
  int w = word.length();
  int s = str.length();
  String ans = "";

  int i = str.indexOf(word);

  while(i >= 0) {                          //keep going until there are no more words
    if (i > 0) ans += str.charAt(i-1);     //get character before word
    if (s > i + w) ans += str.charAt(i+w); // get character after word
    i = str.indexOf(word, i+1);            //find next word
  }
  return ans;
}