feat: kata/even-gray-code

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 | 444 | 606 | 228 | 56 | 82 |
+| 0 | 1 | 2 | 26 | 48 | 445 | 606 | 228 | 56 | 82 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/6-kyu/even-gray-code/README.md

@@ -0,0 +1,39 @@
+# [Even Gray Code](https://www.codewars.com/kata/even-gray-code "https://www.codewars.com/kata/66dc904c177237f5b3e9eb5f")
+
+Background:
+
+The Gray Code is a representation of binary integers in which successive integers differ in only 1 bit. The bit switched at each step is the
+one that yields the smallest value not yet represented. See [Gray Code](https://www.codewars.com/kata/5416ce834c2460b4d300042d).
+
+The *"Even Gray Code"* requires successive binary integers to differ in an **even** number of bits. The bits changed at each step should
+yield the smallest value not yet represented in the standard binary encoding.
+
+Example - The 4-bit Even Gray Code:
+```
+0000 Start at 0
+0011 Switch bits 1,2
+0101 Switch bits 2,3
+0110 Switch bits 1,2
+1001 Switch all 4 bits
+1010 Switch bits 1,2
+1100 Switch bits 2,3
+1111 Switch bits 1,2
+```
+
+Inputs:
+
+The `size` of the Even Gray Code, a integer between 2 and 20.
+
+The `position` where we want the Even Gray Code value, a non-negative integer guaranteed to be smaller than the number of elements in the
+Even Gray Code of length `size`.
+
+Output:
+
+A string representing the value at position `position` of the Even Gray Code of length `size`.
+
+Example:
+
+`even_gray_code(4,5) should return '1010'`, because, as shown above, `1010` is the value of the Even Gray Code of length 4 at position 5.
+(The first position is position 0.)
+
+Source: International Collegiate Programming Contest, North Central North American Regional, 2023.

kata/6-kyu/even-gray-code/main/GrayCode.java

@@ -0,0 +1,5 @@
+interface GrayCode {
+  static String evenGrayCode(int size, int position) {
+    return ("%" + size + "s").formatted(Integer.toBinaryString(position) + Integer.bitCount(position) % 2).replace(' ', '0');
+  }
+}

kata/6-kyu/even-gray-code/test/GrayCodeTest.java

@@ -0,0 +1,23 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class GrayCodeTest {
+  @ParameterizedTest
+  @CsvSource(textBlock = """
+      2, 0, 00
+      2, 1, 11
+      3, 0, 000
+      3, 1, 011
+      3, 2, 101
+      3, 3, 110
+      4, 5, 1010
+      5, 8, 10001
+      10, 230, 0111001101
+      20, 17, 00000000000000100010
+      """)
+  void sample(int size, int position, String code) {
+    assertEquals(code, GrayCode.evenGrayCode(size, position));
+  }
+}

kata/6-kyu/index.md

@@ -133,6 +133,7 @@
 - [Esolang Interpreters #1 - Introduction to Esolangs and My First Interpreter (MiniStringFuck)](esolang-interpreters-number-1-introduction-to-esolangs-and-my-first-interpreter-ministringfuck)
 - [Estimating Amounts of Subsets](estimating-amounts-of-subsets)
 - [Even Fibonacci Sum](even-fibonacci-sum)
+- [Even Gray Code](even-gray-code)
 - [Everybody hates Mondays](everybody-hates-mondays)
 - [Evil Autocorrect Prank](evil-autocorrect-prank)
 - [Experimenting with a sequence of complex numbers](experimenting-with-a-sequence-of-complex-numbers)