Add the 'rotate matrix' algorithm

Author: FSou1

README.md

@@ -31,6 +31,7 @@ An algorithm is a finite sequence of well-defined, computer-implementable instru
   * [Check permutation](src/algorithms/string/permutation) - check if a string is a permutation of the other;
   * [URLify](src/algorithms/string/urlify) - replace all spaces in a string with '%20';
   * [String compression](src/algorithms/string/compression) - perform basic string compression using the counts of repeated characters;
+  * [Rotate matrix](src/algorithms/string/rotate-matrix) - rotate the matrix by 90 degrees;
 * **Sort**
   * [Insertion sort](src/algorithms/sort/insertion/simple) - sort an array with a simple insertion algorithm;
   * [Merge sort](src/algorithms/sort/merge) - sort an array with a merge sort algorithm;

src/algorithms/string/rotate-matrix/README.md

@@ -0,0 +1,6 @@
+# Rotate Matrix
+
+Given an image represented by an NxN matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees. Can you do this in place?
+
+References:
+* https://math.stackexchange.com/questions/1676441/how-to-rotate-the-positions-of-a-matrix-by-90-degrees

src/algorithms/string/rotate-matrix/__test__/rotateMatrix.test.ts

@@ -0,0 +1,17 @@
+import { rotateMatrix } from "../rotateMatrix";
+
+test("rotate matrix is successful", () => {
+  const input = [
+    [1, 1, 1],
+    [2, 2, 2],
+    [3, 3, 3],
+  ];
+
+  const expected = [
+    [3, 2, 1],
+    [3, 2, 1],
+    [3, 2, 1],
+  ];
+  debugger;
+  expect(rotateMatrix(input)).toStrictEqual(expected);
+});

src/algorithms/string/rotate-matrix/rotateMatrix.ts

@@ -0,0 +1,18 @@
+/**
+ * Rotate the matrix by 90 degrees
+ * @param  {number[][]} matrix
+ * @returns number
+ */
+export function rotateMatrix(matrix: number[][]): number[][] {
+  const output = JSON.parse(JSON.stringify(matrix));
+
+  const len = output.length - 1;
+
+  for (let i = 0; i < output.length; i++) {
+    for (let j = 0; j < output.length; j++) {
+      output[j][len - i] = matrix[i][j];
+    }
+  }
+
+  return output;
+}