feat(2022): add challenge 13

Author: borjapazr

2022/challenge-13/README.md

@@ -0,0 +1,42 @@
+# Backups for Santa Claus files
+
+## 🔢 Instructions
+
+To avoid losing data when the server crashes, Santa Claus has decided to make incremental backups. A hacker called S4vitelf is helping him.
+
+On one hand, we have the **timestamp** of when the last backup was made.
+
+We also have the changes that have been made in an array of arrays. Each internal array contains **two elements**: the **id** of the modified file and the **timestamp** of the modification.
+
+You have to create a program that returns an array with the **id^^ of the files that we would have to make backup because they have been modified since the last backup and **sorted in ascending order\*\*. Example:
+
+```javascript
+const lastBackup = 1546300800;
+
+const changes = [
+  [3, 1546301100],
+  [2, 1546300800],
+  [1, 1546300800],
+  [1, 1546300900],
+  [1, 1546301000]
+];
+
+getFilesToBackup(lastBackup, changes); // => [ 1, 3 ]
+// The file with id 1 has been modified twice
+// after the last backup.
+
+// The file with id 2 has not been modified after
+// the last backup.
+
+// The file with id 3 has been modified once
+// after the last backup.
+
+// We have to make a backup
+// of the files 1 and 3.
+```
+
+**Remember that**:
+
+- Returns the id of the files that have been modified after the last backup.
+- Returns an empty array if there are no files to make backup.
+- Remember to sort ids in ascending order.

2022/challenge-13/solution.js

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+const getFilesToBackup = (lastBackup, changes) => {
+  const fileIds = changes.filter(change => change[1] > lastBackup).map(change => change[0]);
+
+  const filesToBackup = new Set(fileIds);
+
+  return [...filesToBackup].sort((fileA, fileB) => fileA - fileB);
+};
+
+export { getFilesToBackup };

2022/challenge-13/solution.spec.js

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+import { getFilesToBackup } from './solution';
+
+describe('Challenge 13: Backups for Santa Claus files', () => {
+  describe('getFilesToBackup(...)', () => {
+    const testCases = [
+      createTestCase(
+        [
+          1546300800,
+          [
+            [2, 1546300800],
+            [3, 1546301100],
+            [1, 1546300800],
+            [1, 1546300900],
+            [1, 1546301000]
+          ]
+        ],
+        [1, 3],
+        'should return an array of file ids that were changed after the last backup (1)'
+      ),
+      createTestCase(
+        [
+          1546300600,
+          [
+            [1, 1546300800],
+            [2, 1546300800],
+            [1, 1546300900],
+            [1, 1546301000],
+            [3, 1546301100]
+          ]
+        ],
+        [1, 2, 3],
+        'should return an array of file ids that were changed after the last backup (2)'
+      ),
+      createTestCase(
+        [
+          1556300600,
+          [
+            [1, 1546300800],
+            [2, 1546300800],
+            [1, 1546300900],
+            [1, 1546301000],
+            [3, 1546301100]
+          ]
+        ],
+        [],
+        'should return an empty array if there are no changes after the last backup'
+      ),
+      createTestCase([1556300600, []], [], 'should return an empty array if there are no changes')
+    ];
+
+    it('#T should return an array', () => {
+      expect(getFilesToBackup(10000, [])).toBeInstanceOf(Array);
+    });
+
+    it.each(testCases)('#$# $description', ({ args, expected }) => {
+      expect(getFilesToBackup(...args)).toEqual(expected);
+    });
+  });
+});

README.md

@@ -69,6 +69,7 @@ This repository contains the solutions to the challenges proposed by [@midudev](
 | 10  |       [The Santa Claus sleigh jump](2022/challenge-10)        |       🟠       | [Show](2022/challenge-10/solution.js) |
 | 11  |       [Santa Claus is Scrum Master](2022/challenge-11)        |       🔴       | [Show](2022/challenge-11/solution.js) |
 | 12  |          [Electric sleighs, wow!](2022/challenge-12)          |       🟠       | [Show](2022/challenge-12/solution.js) |
+| 13  |      [Backups for Santa Claus files](2022/challenge-13)       |       🟢       | [Show](2022/challenge-13/solution.js) |
 
 [^1]: **Difficulty**: 🟢 Easy 🟠 Medium 🔴 Hard 🟣 Very Hard