Java > Recursion-1 > changePi (CodingBat Solution)

Problem:

Given a string, compute recursively (no loops) a new string where all appearances of "pi" have been replaced by "3.14".

changePi("xpix") → "x3.14x"
changePi("pipi") → "3.143.14"
changePi("pip") → "3.14p"


Solution:

public String changePi(String str) {
  if (str.equals("") || str.length() < 2) return str;
  if (str.charAt(0) == 'p' && str.charAt(1) == 'i') 
    return "3.14" + changePi(str.substring(2));
  return str.charAt(0) + changePi(str.substring(1));
}

6 comments:

  1. UnknownSeptember 13, 2017 at 12:11 AM

    if (str.equals("") || str.length() < 2) return str;

    it should be:
    if (str.equals("") || str.length() < 2) return newStr+str;

    ReplyDelete
    Replies
    1. dudeDecember 13, 2018 at 1:49 AM

      No, it should be
      if(str.length() < 2) return str;

      Delete
  2. dudeDecember 13, 2018 at 1:47 AM

    public String changePi(String str) {
    if(str.length() < 2) return str;
    if(str.substring(0, 2).equals("pi")) return "3.14" + changePi(str.substring(2));
    return str.charAt(0) + changePi(str.substring(1));

    ReplyDelete
  3. UnknownDecember 23, 2018 at 6:24 AM

    Thanks a lot searching for this.

    ReplyDelete
  4. ioannisaDecember 10, 2019 at 2:40 AM

    public String changePi(String str) {
    int idx = str.indexOf("pi");
    if (idx==-1)
    return str;

    return changePi(str.substring(0,idx)+"3.14"+str.substring(idx+2));
    }

    ReplyDelete
  5. UnknownApril 27, 2021 at 11:10 PM

    public String changePi(String str) {
    if(str.equals(""))
    return str;
    else if(str.startsWith("pi"))
    return "3.14"+changePi(str.substring(2));
    else return str.charAt(0)+changePi(str.substring(1));

    }

    ReplyDelete