feat: kata/parse-a-linked-list-from-a-string

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 | 431 | 591 | 219 | 56 | 79 |
+| 0 | 1 | 2 | 26 | 48 | 432 | 591 | 219 | 56 | 79 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/6-kyu/index.md

@@ -255,6 +255,7 @@
 - [Page replacement algorithms: LRU](page-replacement-algorithms-lru)
 - [Pair of gloves](pair-of-gloves)
 - [Parabolic Arc Length](parabolic-arc-length)
+- [Parse a linked list from a string](parse-a-linked-list-from-a-string)
 - [Parse bank account number](parse-bank-account-number)
 - [Parse HTML/CSS Colors](parse-html-slash-css-colors)
 - [Pascal's Triangle](pascals-triangle)

kata/6-kyu/parse-a-linked-list-from-a-string/README.md

@@ -0,0 +1,43 @@
+# [Parse a linked list from a string](https://www.codewars.com/kata/parse-a-linked-list-from-a-string "https://www.codewars.com/kata/582c5382f000e535100001a7")
+
+## Task
+
+Create a function `parse` which accepts exactly one argument `string` / `$string` / `s` / `strrep` ( or similar, depending on the language )
+which is a string representation of a linked list. Your function must return the corresponding linked list, constructed from instances of
+the `Node` class/struct/type. The string representation of a list has the following format: the value of the node, followed by a whitespace,
+an arrow and another whitespace (`" -> "`), followed by the rest of the linked list. Each string representation of a linked list will end in
+`"null"` / `"NULL"` / `"nil"` / `"nullptr"` / `"null()"` depending on the language you are undertaking this Kata in. For example, given the
+following string representation of a linked list:
+
+```
+new Node(1, new Node(2, new Node(3)))
+```
+
+Note that due to the way the constructor for `Node` is defined, if a second argument is not provided, the `next` / `$next` / `Next` field is
+automatically set to `null` / `NULL` / `nil` / `nullptr` ( or equivalent in your language ). That means your function could also return the
+following ( if it helps you better visualise what is actually going on ):
+
+```
+new Node(1, new Node(2, new Node(3, null)))
+```
+
+Another example: given the following string input:
+
+```
+"0 -> 1 -> 4 -> 9 -> 16 -> null"
+```
+
+... your function should return:
+
+```
+new Node(0, new Node(1, new Node(4, new Node(9, new Node(16)))))
+```
+
+If the input string is just `"null"` / `"NULL"` / `"nil"` / `"nullptr"` / `"null()"`, return `null` / `NULL` / `nil` / `nullptr` /
+`null()` / `[]` ( or equivalent ).
+
+For the simplicity of this Kata, the values of the nodes in the string representation will always ever be **non-negative integers**, so the
+following would **not** occur: `"Hello World -> Goodbye World -> 123 -> null"` / `"Hello World -> Goodbye World -> 123 -> NULL"` /
+`"Hello World -> Goodbye World -> 123 -> nil"` / `"Hello World -> Goodbye World -> 123 -> nullptr"` ( depending on the language ). This also
+means that the values of each `Node` must also be **non-negative integers** so keep that in mind when you are parsing the list from the
+string.

kata/6-kyu/parse-a-linked-list-from-a-string/main/Kata.java

@@ -0,0 +1,10 @@
+interface Kata {
+  static Node parseLinkedList(String str) {
+    Node head = null;
+    String[] values = str.split(" -> ");
+    for (int i = values.length - 2; i >= 0; i--) {
+      head = new Node(Integer.parseInt(values[i]), head);
+    }
+    return head;
+  }
+}

kata/6-kyu/parse-a-linked-list-from-a-string/main/Node.java

@@ -0,0 +1,9 @@
+import lombok.AllArgsConstructor;
+import lombok.RequiredArgsConstructor;
+
+@AllArgsConstructor
+@RequiredArgsConstructor
+class Node {
+  final int data;
+  Node next;
+}

kata/6-kyu/parse-a-linked-list-from-a-string/test/SolutionTest.java

@@ -0,0 +1,21 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+  @Test
+  void sample() {
+    var n1 = Kata.parseLinkedList("1 -> null");
+    assertEquals(1, n1.data);
+    assertNull(n1.next);
+
+    var n2 = Kata.parseLinkedList("1 -> 2 -> 3 -> null");
+    assertEquals(1, n2.data);
+    assertEquals(2, n2.next.data);
+    assertEquals(3, n2.next.next.data);
+    assertNull(n2.next.next.next);
+
+    assertNull(Kata.parseLinkedList("null"));
+  }
+}