feat(7-kyu): kata/bubblesort-once (#456)

* feat(7-kyu): kata/bubblesort-once

* test: cover already sorted array case

Author: ParanoidUser

docs/README.md

@@ -1,7 +1,7 @@
 # Codewars Handbook ☕️🚀
 
 [![Views statistics +1 👀](https://img.shields.io/badge/dynamic/xml?color=success&label=views&query=//*[name()=%27text%27][3]&url=https://hits.seeyoufarm.com/api/count/incr/badge.svg?url=https%3A%2F%2Fgithub.com%2FParanoidUser%2Fcodewars-handbook)](https://hits.seeyoufarm.com/api/count/graph/dailyhits.svg?url=https://github.com/ParanoidUser/codewars-handbook)
-[![Solved kata 👌](https://img.shields.io/badge/solved%20kata-1374-red.svg)](https://www.codewars.com/kata/search/java)
+[![Solved kata 👌](https://img.shields.io/badge/solved%20kata-1375-red.svg)](https://www.codewars.com/kata/search/java)
 [![CI pipeline 🛠](https://img.shields.io/github/actions/workflow/status/ParanoidUser/codewars-handbook/build.yml?branch=main)](https://github.com/ParanoidUser/codewars-handbook/actions/workflows/build.yml)
 [![Quality gate 🔎](https://img.shields.io/sonar/alert_status/codewars-handbook?server=https%3A%2F%2Fsonarcloud.io)](https://sonarcloud.io/dashboard?id=codewars-handbook)
 [![Let's have a chat! 📞](https://img.shields.io/gitter/room/ParanoidUser/codewars-handbook?color=49c39e)](https://gitter.im/ParanoidUser/codewars-handbook)
@@ -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) |
 |:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:---------------------------:|:---------------------------------:|
-|               -               |               1               |               2               |              22               |              40               |              413              |              556              |              205              |             58              |                76                 |
+|               -               |               1               |               2               |              22               |              40               |              413              |              557              |              205              |             58              |                76                 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/7-kyu/bubblesort-once/README.md

@@ -0,0 +1,42 @@
+# [Bubblesort Once](https://www.codewars.com/kata/bubblesort-once "https://www.codewars.com/kata/56b97b776ffcea598a0006f2")
+
+## Overview
+
+[Bubblesort](https://en.wikipedia.org/wiki/Bubble_sort) is an inefficient sorting algorithm that is
+simple to understand and therefore often taught in introductory computer science courses as an
+example how _not_ to sort a list. Nevertheless, it is correct in the sense that it eventually
+produces a sorted version of the original list when executed to completion.
+
+At the heart of Bubblesort is what is known as a _pass_. Let's look at an example at how a pass
+works.
+
+Consider the following list:
+
+```
+9, 7, 5, 3, 1, 2, 4, 6, 8
+```
+
+We initiate a pass by comparing the first two elements of the list. Is the first element greater
+than the second? If so, we swap the two elements. Since `9` is greater than `7` in this case, we
+swap them to give `7, 9`. The list then becomes:
+
+```
+7, 9, 5, 3, 1, 2, 4, 6, 8
+```
+
+We then continue the process for the 2nd and 3rd elements, 3rd and 4th elements ... all the way up
+to the last two elements. When the pass is complete, our list becomes:
+
+```
+7, 5, 3, 1, 2, 4, 6, 8, 9
+```
+
+Notice that the largest value `9` "bubbled up" to the end of the list. This is precisely how
+Bubblesort got its name.
+
+## Task
+
+Given an array of integers, your function `bubblesortOnce`/`bubblesort_once`/`BubblesortOnce` (or
+equivalent, depending on your language's naming conventions) should return a *new* array equivalent
+to performing exactly **1 complete pass** on the original array. Your function should be pure, i.e.
+it should **not** mutate the input array.

kata/7-kyu/bubblesort-once/main/BubblesortOnce.java

@@ -0,0 +1,13 @@
+interface BubblesortOnce {
+  static int[] bubbleSortOnce(int[] array) {
+    int[] copy = array.clone();
+    for (int i = 0; i < copy.length - 1; i++) {
+      if (copy[i] > copy[i + 1]) {
+        copy[i] += copy[i + 1];
+        copy[i + 1] = copy[i] - copy[i + 1];
+        copy[i] -= copy[i + 1];
+      }
+    }
+    return copy;
+  }
+}

kata/7-kyu/bubblesort-once/test/SolutionTest.java

@@ -0,0 +1,11 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+class SolutionTest {
+  @Test
+  void sample() {
+    assertArrayEquals(new int[]{7, 5, 3, 1, 2, 4, 6, 8, 9}, BubblesortOnce.bubbleSortOnce(new int[]{9, 7, 5, 3, 1, 2, 4, 6, 8}));
+    assertArrayEquals(new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9}, BubblesortOnce.bubbleSortOnce(new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9}));
+  }
+}

kata/7-kyu/index.md

@@ -58,6 +58,7 @@
 - [Bits Battle](bits-battle)
 - [Breaking chocolate problem](breaking-chocolate-problem)
 - [Broken sequence](broken-sequence)
+- [Bubblesort Once](bubblesort-once)
 - [Build a square](build-a-square)
 - [Building blocks](building-blocks)
 - [Bulls and Cows](bulls-and-cows)