feat: kata/zeta-swap

docs/README.md

@@ -25,7 +25,7 @@ slug.
 
 | [1 kyu](/kata/1-kyu/index.md) | [2 kyu](/kata/2-kyu/index.md) | [3 kyu](/kata/3-kyu/index.md) | [4 kyu](/kata/4-kyu/index.md) | [5 kyu](/kata/5-kyu/index.md) | [6 kyu](/kata/6-kyu/index.md) | [7 kyu](/kata/7-kyu/index.md) | [8 kyu](/kata/8-kyu/index.md) | [beta](/kata/beta/index.md) | [retired](/kata/retired/index.md) |
 |:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:---------------------------:|:---------------------------------:|
-| 0 | 1 | 2 | 26 | 48 | 445 | 606 | 228 | 58 | 82 |
+| 0 | 1 | 2 | 26 | 48 | 445 | 606 | 228 | 59 | 82 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/beta/index.md

@@ -73,3 +73,5 @@
 - [Who's Next in Line?](whos-next-in-line)
 # Y
 - [Your Basic FizzBuzz kata](your-basic-fizzbuzz-kata)
+# Z
+- [Zeta Swap](zeta-swap)

kata/beta/zeta-swap/README.md

@@ -0,0 +1,21 @@
+# [Zeta Swap](https://www.codewars.com/kata/zeta-swap "https://www.codewars.com/kata/6780126afa635e648148397e")
+
+Hello Detective! The Ministry of Magic has suddenly fallen while we were in the middle of our annual Tetrawizard Tournament. A murder has
+been spotted within the chambers of Slytherin. Our only witness is Ron. But, as you know, Ron was preoccupied with Lavendar while it
+happened. He is unsure what letter he saw on the back of the coats of the suspects since he reads right to left.
+
+Your task is to implement a function that takes a string and swaps each letter with its "opposite" in the alphabet (e.g., 'a' ↔ 'z', 'b' ↔ 'y', etc.),
+but only if the letter occurs more than once in the string.
+
+- Non-alphabet characters (e.g., numbers, punctuation, whitespace) should remain unchanged.
+- The function should preserve the case of the letters (e.g., 'A' ↔ 'Z', 'b' ↔ 'y').
+- Single-occurrence letters are not swapped.
+
+Input
+
+- A string containing alphabetic and non-alphabetic characters.
+- Length of the string: 0 ≤ length ≤ 10^5.
+
+Output
+
+- A string with swapped letters where applicable, and all other characters unchanged.

kata/beta/zeta-swap/main/ZetaSwap.java

@@ -0,0 +1,10 @@
+import static java.util.stream.Collectors.counting;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.joining;
+
+interface ZetaSwap {
+  static String swapMurder(String suspects) {
+    var count = suspects.chars().boxed().collect(groupingBy(c -> c | 32, counting()));
+    return suspects.chars().mapToObj(c -> "" + (char) (Character.isLetter(c) && count.get(c | 32) > 1 ? (c > 96 ? 219 : 155) - c : c)).collect(joining());
+  }
+}

kata/beta/zeta-swap/test/SolutionTest.java

@@ -0,0 +1,18 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class SolutionTest {
+  @ParameterizedTest
+  @CsvSource(textBlock = """
+      abcabc, zyxzyx
+      aabc, zzbc
+      abc, abc
+      HeLLo, HeOOo
+      123 !@# aabc, 123 !@# zzbc
+      """)
+  void sample(String suspects, String swapped) {
+    assertEquals(swapped, ZetaSwap.swapMurder(suspects));
+  }
+}