# changeXy challenge

Hi,

I am working on below challenge
http://codingbat.com/prob/p101372

Psedo code:
1. if array length is zero return 0
2. if array length is 1 and it is x return x
3. if array length is 1 and it is not x return same str
4. else find location of x and replace with y if greater than length
5. return replaced string
I wrote my code as below

``````public String changeXY(String str) {
if(str.length()==0){
return "";
}
if(str.length()==1&&"x".equals(str)){
return "y";
}
if(str.length()==1&&!"x".equals(str)){
return str;
}
if(str.length()>1){
return str.replace('x','y');
}

return null;
}
``````

I am  passing all tests

How to improve/modify my design, code and any other alternate approaches. please advise
LVL 7
###### Who is Participating?

Commented:
The instructions say you have to do this challenge recursively.
What would happen if you modified your code to just call replace without all those if statements?
0

Commented:
0

Commented:
>> No recursion is necessary for this challenge.
You are already stating what the author has observed.
But the challenge is to learn how to use recursion.
0

Commented:
@phoffric,  gudii9 has already gone through 11 recursion challenges last week.  He will not learn anything by using recursion when it is not useful.  He really needs to learn the API better.
0

Commented:
I'm sorry. I was wrong.   Your choice of the replace method is fine.
0

Author Commented:
any improvements or alternate approaches for this challenge?
0

Commented:
Phoffric, told you in the first comment above here.  He asked you a question about line 12 of your code.
0

Commented:
Before advising upon improvement, we first need to see your recursive solution to the challenge.
0

Author Commented:
``````public String changeXY(String str) {
if (str.length() == 0){
return str;

}
else if (str.charAt(0) == 'x') {
return "y" + changeXY(str.substring(1));

}
else{
return str.charAt(0) + changeXY(str.substring(1));

}
}
``````
above passes all tests. any improvements or alternate approaches?
0

Author Commented:
``````public String changeXY(String str) {
String regex="x";
String substr="y";
String str2 = str.replaceAll(regex, substr);
return str2;
}
``````

above also passed all tests
0

Commented:
Good work!
Here is my code.
``````public String changeXY(String str) {
int index = str.indexOf("x");
if(index == -1)return str;
return changeXY(str.substring(0, index) + "y" + str.substring(index + 1));
}
``````

``````public String changeXY(String str) {
return str.replaceAll("x", "y");
}
``````
0

Author Commented:
i like index method approach where u are finding index of x then substring just until  x and concatinating with y(replacement of x) then concatenating later part of string as it is.

also your regex approach of replaceAll is more short
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.