pairstar challenge

Posted on 2016-09-21
Last Modified: 2016-09-22

I am working on below challenge.
Psedo code:
1. check the array length 0  or 1 then retun same str
2.else return string with * in between for repeated pair of characters

I wrote my code as below and not passing all tests
public String pairStar(String str) {
    return str;
  return str.charAt(0)+"*"+pairStar(str.substring(1));


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Expected      Run            
pairStar("hello") → "hel*lo"      "h*e*l*l*o"      X      
pairStar("xxyy") → "x*xy*y"      "x*x*y*y"      X      
pairStar("aaaa") → "a*a*a*a"      "a*a*a*a"      OK      
pairStar("aaab") → "a*a*ab"      "a*a*a*b"      X      
pairStar("aa") → "a*a"      "a*a"      OK      
pairStar("a") → "a"      "a"      OK      
pairStar("") → ""      ""      OK      
pairStar("noadjacent") → "noadjacent"      "n*o*a*d*j*a*c*e*n*t"      X      
pairStar("abba") → "ab*ba"      "a*b*b*a"      X      
pairStar("abbba") → "ab*b*ba"      "a*b*b*b*a"      X      
other tests

Any improvements or alternate approaches?      

please advise
Question by:gudii9
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Author Comment

ID: 41809272
public String pairStar(String str) {
    return str;
  else if(str.charAt(0)==str.charAt(1)){
  return str.charAt(0)+"*"+pairStar(str.substring(1));
  return str.charAt(0)+pairStar(str.substring(1));

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above passed all tests. any improvements or alternate approaches?
LVL 27

Accepted Solution

rrz earned 500 total points
ID: 41809535
Your code is good. Personally, I would clean it up a little.
public String pairStar(String str) {
  if(str.length() < 2){
    return str;
  if(str.charAt(0) == str.charAt(1)){
    return str.charAt(0) + "*" + pairStar(str.substring(1));
  return str.charAt(0) + pairStar(str.substring(1));

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