Add the 'check permutation' algorithms

Author: FSou1

README.md

@@ -28,6 +28,7 @@ An algorithm is a finite sequence of well-defined, computer-implementable instru
 * **String**
   * [Document distance](src/algorithms/string/document-distance) - measure similarity between two strings;
   * [Is unique](src/algorithms/string/unique) - check a string for uniqueness;
+  * [Check permutation](src/algorithms/string/permutation) - check if a string is a permutation of the other;
 * **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/permutation/README.md

@@ -0,0 +1,13 @@
+# Check Permutation
+
+Given two st4rings, write a method to decide if one is a permutation of the other.
+
+## permutationV1
+
+This algorithm uses additional memory which gives you `O(n)` time and `O(n)` memory.
+
+## permutationV2
+
+This algorithm does not use additional memory but alters the input. This one gives you `O(n * log n)` time (depends on the sorting algorithm you choose).
+
+1, 84, 122, 131

src/algorithms/string/permutation/__tests__/permutations.test.ts

@@ -0,0 +1,16 @@
+import { permutationsV1 } from "../permutationsV1";
+import { permutationsV2 } from "../permutationsV2";
+
+test.each([
+  ["abc", "cab", true],
+  ["aaaaaaaaaaaaaaa", "bbbbbbbb", false]
+])("#1 the string %p is the permutation of the string %p: %p", (a, b, value) => {
+  expect(permutationsV1(a, b)).toBe(value);
+});
+
+test.each([
+  ["abc", "cab", true],
+  ["aaaaaaaaaaaaaaa", "bbbbbbbb", false]
+])("#2 the string %p is the permutation of the string %p: %p", (a, b, value) => {
+  expect(permutationsV2(a, b)).toBe(value);
+});

src/algorithms/string/permutation/permutationsV1.ts

@@ -0,0 +1,23 @@
+/**
+ * Check if the string a is a permutation of the string b
+ * @param  {string} a
+ * @param  {string} b
+ * @returns boolean
+ */
+export function permutationsV1(a: string, b: string): boolean {
+    if(a === b) {
+        return true;
+    }
+
+    if(a.length !== b.length) {
+        return false;
+    }
+
+    const dict = {};
+    for(let i = 0, j = a.length; i < j; i++) {
+        dict[a[i]] = (dict[a[i]] || 0) + 1;
+        dict[b[i]] = (dict[b[i]] || 0) + 1;
+    }
+
+    return !Object.values(dict).find((v: number) => v % 2 != 0);
+}

src/algorithms/string/permutation/permutationsV2.ts

@@ -0,0 +1,23 @@
+import { sort } from "../../sort/heap/heapSort";
+
+/**
+ * Check if the string a is a permutation of the string b
+ * @param  {string} a
+ * @param  {string} b
+ * @returns boolean
+ */
+export function permutationsV2(a: string, b: string): boolean {
+  const combined = a.split("")
+    .concat(b.split(""))
+    .map((el) => el.charCodeAt(0));
+
+  const sorted = sort(combined);
+
+  for (let i = 0, j = combined.length; i < j; i += 2) {
+    if (sorted[i] != sorted[i + 1]) {
+      return false;
+    }
+  }
+
+  return true;
+}

tsconfig.json

@@ -1,7 +1,7 @@
 {
   "compilerOptions": {
       "module": "commonjs",
-      "target": "es6",
+      "target": "ESNext",
       "noImplicitAny": false,
       "sourceMap": false,
       "rootDir": "src",