question: flip

README.md

@@ -111,6 +111,7 @@ I started this in the [issue #176](https://buttondown.email/cassidoo/archive/we-
 
 - [333 - happyNewYear](src/2024/333-happyNewYear)
 - [334 - letters](src/2024/334-letters)
+- [335 - flip](src/2024/335-flip)
 </details>
 
 ## Installing & Running

src/2024/335-flip/README.md

@@ -0,0 +1,35 @@
+# flip
+
+Interview question of the [issue #335 of rendezvous with cassidoo](https://buttondown.email/cassidoo/archive/try-and-fail-but-dont-fail-to-try-john-quincy/).
+
+## The Question
+
+**Given a 2D array, write a function that flips it vertically or horizontally.**
+
+Example:
+
+```js
+let array = [
+	[1, 2, 3],
+	[4, 5, 6],
+	[7, 8, 9]
+]
+
+> flip(array, 'horizontal')
+> [
+	[3, 2, 1],
+	[6, 5, 4],
+	[9, 8, 7]
+]
+
+> flip(array, 'vertical')
+> [
+	[7, 8, 9],
+	[4, 5, 6],
+	[1, 2, 3]
+]
+```
+
+## Installing & Running
+
+Just `pnpm i` to install all dependencies and then `pnpm t` to run the tests!

src/2024/335-flip/flip.test.ts

@@ -0,0 +1,29 @@
+import { flip } from './flip';
+
+describe('#flip', () => {
+	it('should flip the array horizontally', () => {
+		const array = [
+			[1, 2, 3],
+			[4, 5, 6],
+			[7, 8, 9],
+		];
+		expect(flip(array, 'horizontal')).toStrictEqual([
+			[3, 2, 1],
+			[6, 5, 4],
+			[9, 8, 7],
+		]);
+	});
+
+	it('should flip the array vertically', () => {
+		const array = [
+			[1, 2, 3],
+			[4, 5, 6],
+			[7, 8, 9],
+		];
+		expect(flip(array, 'vertical')).toStrictEqual([
+			[7, 8, 9],
+			[4, 5, 6],
+			[1, 2, 3],
+		]);
+	});
+});

src/2024/335-flip/flip.ts

@@ -0,0 +1,52 @@
+/*
+Given a 2D array, write a function that flips it vertically or horizontally.
+
+Example:
+
+let array = [
+	[1, 2, 3],
+	[4, 5, 6],
+	[7, 8, 9]
+]
+
+> flip(array, 'horizontal')
+> [
+	[3, 2, 1],
+	[6, 5, 4],
+	[9, 8, 7]
+]
+
+> flip(array, 'vertical')
+> [
+	[7, 8, 9],
+	[4, 5, 6],
+	[1, 2, 3]
+]
+*/
+
+type Matrix = number[][];
+
+function flipHorizontally(matrix: Matrix): Matrix {
+	return matrix.map(row => row.toReversed());
+}
+
+function transpose(matrix: Matrix) {
+	const transposed: Matrix = [];
+	for (let i = 0; i < matrix.length; i++) {
+		const column: number[] = [];
+
+		for (let j = 0; j < matrix[i].length; j++) {
+			column.push(matrix[j][i]);
+		}
+
+		transposed.push(column);
+	}
+	return transposed;
+}
+
+export function flip(matrix: Matrix, direction: 'horizontal' | 'vertical'): Matrix {
+	if (direction === 'horizontal') {
+		return flipHorizontally(matrix);
+	}
+	return transpose(flipHorizontally(transpose(matrix)));
+}