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 :

countHi - Recursive

Given a string, compute recursively (no loops) the number of times lowercase "hi" appears in the string. countHi("xxhixx") → 1 countHi("xhixhix") → 2 countHi("hi") → 1

C# :

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public static int countHi(String str) { //stop condition if (str.Length < 2) return 0; //Process int index = str.IndexOf("hi"); if (index < 0) return 0; return 1 + countHi(str.Substring(index + 1, str.Length - (1 + index))); }

Result :