Java > Recursion-1 > strCount (CodingBat Solution)

Problem:

Given a string and a non-empty substring sub, compute recursively the number of times that sub appears in the string, without the sub strings overlapping.

strCount("catcowcat", "cat") → 2
strCount("catcowcat", "cow") → 1
strCount("catcowcat", "dog") → 0


Solution:

public int strCount(String str, String sub) {
  int strlen = str.length();
  int sublen = sub.length();
  if (strlen < sublen) return 0;
  if (str.substring(0,sublen).equals(sub))
    return 1 + strCount(str.substring(sublen), sub);
  else 
    return strCount(str.substring(1), sub);
}

6 comments:

  1. UnknownNovember 3, 2015 at 1:56 PM

    if (!str.contains(sub)) return 0;
    else return 1 + strCount(str.substring(str.indexOf(sub)+sub.length()), sub);

    ReplyDelete
    Replies
    1. AnonymousJune 27, 2016 at 2:11 PM

      If we're going to use any old java.lang.string method, might as well defeat the purpose of this exercise entirely and not even bother with recursion:

      String s=str.replace(sub,"");
      return (str.length()-s.length())/sub.length();

      Delete
  2. AnonymousOctober 14, 2016 at 4:09 AM

    public int strCount(String str, String sub) {
    if(str.indexOf(sub)==-1) return 0;
    if(str.indexOf(sub)!=-1)
    {
    return 1 + strCount(str.substring(str.indexOf(sub)+sub.length()), sub);
    }
    return 0;
    }

    ReplyDelete
  3. UnknownSeptember 5, 2017 at 2:22 AM

    if(str.equals("")) return 0;
    if(str.startsWith(sub)) return 1 + strCount(str.substring(sub.length()), sub);
    return strCount(str.substring(1), sub);

    ReplyDelete
  4. AnonymousSeptember 18, 2020 at 4:23 AM

    public int strCount(String str, String sub) {
    if(str.isEmpty()){
    return 0;
    }
    if(str.startsWith(sub)){
    return 1 + strCount(str.substring(sub.length()), sub);
    }
    return strCount(str.substring(1), sub);
    }

    ReplyDelete
  5. AnonymousSeptember 18, 2020 at 4:24 AM

    public int strCount(String str, String sub) {
    if(str.isEmpty()){
    return 0;
    }
    return (str.startsWith(sub))?
    1 + strCount(str.substring(sub.length()), sub)
    : strCount(str.substring(1), sub);
    }

    ReplyDelete