Given a string, return recursively a "cleaned" string where adjacent chars that are the same have been reduced to a single char. So "yyzzza" yields "yza". stringClean("yyzzza") → "yza" stringClean("abbbcdd") → "abcd" stringClean("Hello") → "Helo"

Solution1 :

public String stringClean(String str)
{
    if(str.length()<2)  
    {
      return "";
    }
    else if(str.charAt(0)==str.charAt(1))
    {
      return stringClean(str.substring(1));
    }
    else
    {
      return str.charAt(0)+stringClean(str.substring(1));
    }
}


solution 2: with out using substring function


public String stringClean(String str)
{
    String res  = new String();
    return clean(str,0);
}

public String clean(String str,int index)
{
  if(str.length()-index<2)  
    {
      return str.valueOf(str.charAt(index));
    }
    else if(str.charAt(index)==str.charAt(index+1))
    {
      return clean(str,index+1);
    }
    else
    {
      return str.charAt(index)+clean(str,index+1);
    }
}