CodingBat: Recursion-1 > pairStar prev | next | chance Given a string, compute recursively a new string where identical chars that are adjacent in the original string are separated from each other by a "*". pairStar("hello") → "hel*lo" pairStar("xxyy") → "x*xy*y" pairStar("aaaa") → "a*a*a*a"

PairStar.java

class PairStar{
  public static void main(String ... args){
    System.out.println(pairStar(args[0]));
  }
  public static String pairStar(String str) {
    System.out.println(str);
    if(str.length()<=1){
      return str;
    }
    int mid= str.length()/2;
    String str1=pairStar(str.substring(0,mid));
    String str2=pairStar(str.substring(mid,str.length()));
    // System.out.println();
    char c;
    if((c=str1.charAt(str1.length()-1))==str2.charAt(0)){
      return str1+"*"+str2;
    }else{
      return str1+str2;
    }
  }

}