Java > Recursion-1 > countHi2 (CodingBat Solution)

Problem:

Given a string, compute recursively the number of times lowercase "hi" appears in the string, however do not count "hi" that have an 'x' immedately before them.

countHi2("ahixhi") → 1
countHi2("ahibhi") → 2
countHi2("xhixhi") → 0


Solution:

public int countHi2(String str) {
  int len = str.length();
  if (len < 2) return 0;
  if (str.substring(len-2, len).equals("hi")) {
    if ((len > 2 && str.charAt(len-3) != 'x') || len == 2 )
      return 1 + countHi2(str.substring(0, len-1));
  }
  return countHi2(str.substring(0, len-1));
  
}

12 comments:

  1. UnknownFebruary 15, 2015 at 5:51 PM

    here is a simple solution :

    public int countHi2(String str) {
    return (str.length() < 2)?0:
    (str.substring(0,2).equals("xh"))?
    countHi2(str.substring(2)):
    (str.substring(0,2).equals("hi"))?
    1 + countHi2(str.substring(1)):
    countHi2(str.substring(1));
    }

    ReplyDelete
  2. UnknownSeptember 7, 2015 at 5:35 AM

    static int countHi2(String str) {
    if(str.length()<3)return 0;
    int count=0;
    if(Pattern.matches("[a-w[y-z]]hi",str.substring(str.length()-3,str.length())))
    count=1;
    return count+countHi2(str.substring(0,str.length()-1));

    }

    ReplyDelete
  3. UnknownSeptember 22, 2019 at 4:28 PM

    I found it easier to use a private helper method

    public int countHi2(String str) {

    return countHi2Help(str, ' ');

    }

    private int countHi2Help(String str, Character c)
    {
    if(str.length()<=1)
    return 0;

    int x = 0;
    String sub = str.substring(0, 2);
    if(sub.equalsIgnoreCase("hi") && c!='x')
    x++;

    return x + countHi2Help(str.substring(1,str.length()), str.charAt(0));
    }

    ReplyDelete
  4. UnknownJanuary 4, 2020 at 6:32 AM

    str=str.replaceAll("xhi","");
    if(str.length() <= 1 ) return 0;
    if(str.substring(0,2).equals("hi") )
    return 1 + countHi2(str.substring(1));
    else
    return countHi2(str.substring(1));

    ReplyDelete
  5. ad aFebruary 27, 2020 at 8:26 PM

    if (str.equals("hi")) return 1;
    if (str.length() < 3) return 0;

    if (str.substring(0,3).equals("xhi")) return countHi2(str.substring(3));

    if (str.substring(0,2).equals("hi")) return 1 + countHi2(str.substring(2));

    return countHi2(str.substring(1));

    ReplyDelete
  6. UnknownJuly 27, 2020 at 12:43 PM

    public int countHi2(String str) {
    if (str.length() < 2)
    {
    return 0;
    }
    else
    {
    if (str.substring(0, 2).equals("hi"))
    {
    return 1 + countHi2(str.substring(2));
    }
    else if (str.charAt(0) == 'x' && (3 <= str.length() && str.substring(1, 3).equals("hi")))
    {
    return countHi2(str.substring(3));
    }
    else
    {
    return countHi2(str.substring(1));
    }
    }
    }

    ReplyDelete
  7. AnonymousSeptember 16, 2020 at 6:35 AM

    public int countHi2(String str) {
    if (str.length() <= 1){
    return 0;
    }
    if (str.charAt(0) == 'x' && str.charAt(1) == 'h'){
    return countHi2(str.substring(2));
    }
    if (str.charAt(0) == 'h' && str.charAt(1) == 'i'){
    return 1 + countHi2(str.substring(2));
    }
    return countHi2(str.substring(1));
    }

    ReplyDelete
  8. UnknownDecember 4, 2021 at 7:38 AM

    Simple to understand this I guess.

    public int countHi2(String str) {
    if (str.equals("") || str.length()<2) return 0;
    if (str.length()>2 && str.substring(0,3).equals("xh")){
    return countHi2(str.substring(2));
    }
    if (str.length()>2 && str.substring(0,3).equals("xhi")){
    return countHi2(str.substring(3));
    }
    else if (str.length()>1 && str.substring(0,2).equals("hi")){
    return 1+countHi2(str.substring(2));
    }
    return countHi2(str.substring(1));
    }

    ReplyDelete
  9. UnknownFebruary 6, 2022 at 4:30 PM

    if(str.equals("hi")) return 1;
    if(str.length()<3) return 0;
    if(str.substring(0,3).equals("xhi")) return countHi2(str.substring(3));
    if(str.substring(0,2).equals("hi")) return 1 + countHi2(str.substring(2));
    return countHi2(str.substring(1));

    ReplyDelete
  10. UnknownApril 16, 2022 at 10:41 AM

    public int countHi2(String str) {
    if (str.length() == 0) {
    return 0;
    }
    if (str.startsWith("hi")) {
    return 1 + countHi2(str.substring(1));
    }
    if (str.startsWith("xhi")) {
    return countHi2(str.substring(2));
    }
    return countHi2(str.substring(1));
    }

    ReplyDelete
  11. AvengerSeptember 17, 2022 at 10:35 AM

    public int countHi2(String str)
    {
    if(str.length() < 2)
    {
    return 0;
    }
    if(str.startsWith("hi"))
    {
    return 1+countHi2(str.substring(1));
    }
    if(str.startsWith("xhi"))
    {
    return 0+countHi2(str.substring(2));
    }
    return countHi2(str.substring(1));
    }

    ReplyDelete