changePi - Recursive - Java & C#

Given a string, compute recursively (no loops) a new string where all appearances of "pi" have been replaced by "3.14".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

Java :

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public String changePi(String str) { if (str.length() < 1) return ""; int index = str.indexOf("pi"); if (index < 0) return str; String temp = str.substring(0, index); return temp+"3.14"+changePi(str.substring(index+2, str.length())); }

Test result:

C# :

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public static String changePi(String str) { if (str.Length < 1) return ""; int index = str.IndexOf("pi"); if (index < 0 ) return str; String temp0 = str.Substring(0, index); String temp = str.Substring(index+2, str.Length-(2+index)); return temp0+"3.14" + changePi(temp); }

Test Result :

changeXY - Recursive - Java & C#

Given a string, compute recursively (no loops) a new string where all the lowercase 'x' chars have been changed to 'y' chars.

changeXY("codex") → "codey"
changeXY("xxhixx") → "yyhiyy"
changeXY("xhixhix") → "yhiyhiy"
Java :

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public String changeXY(String str) { if(str.length() < 1) return ""; char temp = str.charAt(str.length()-1); if(temp == 'x') temp = 'y'; return changeXY(str.substring(0,str.length()-1))+temp; }

Test Result:

C#:

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public static String changeXY(String str) { if (str.Length < 1) return ""; Char temp = str[str.Length - 1]; if (temp == 'x') temp = 'y'; return changeXY(str.Substring(0, str.Length - 1)) + temp; }

Test Result :