Fix GeneratePermutations so that it actually returns the permutations instead of logging them + add Jest test.

Author: lvlte

Backtracking/GeneratePermutations.js

@@ -1,8 +1,8 @@
 /*
- * Problem Statement: Generate all distinct permutations of a string/array (all permutations should be in sorted order);
+ * Problem Statement: Generate all distinct permutations of a an array (all permutations should be in sorted order);
  *
  * What is permutations?
- * - Permutation means possible arrangements in a set (here it is string/array);
+ * - Permutation means possible arrangements in a set (here it is an array);
  *
  * Reference to know more about permutations:
  * - https://www.britannica.com/science/permutation
@@ -17,17 +17,21 @@ const swap = (arr, i, j) => {
  return newArray
 }
 
-const permutations = (arr, low, high) => {
- if (low === high) {
- console.log(arr.join(' '))
- return
- }
- for (let i = low; i <= high; i++) {
- arr = swap(arr, low, i)
- permutations(arr, low + 1, high)
+const permutations = arr => {
+ let P = []
+ const permute = (arr, low, high) => {
+ if (low === high) {
+ P.push([...arr])
+ // console.log(arr.join(' '))
+ return P
+ }
+ for (let i = low; i <= high; i++) {
+ arr = swap(arr, low, i)
+ permute(arr, low + 1, high)
+ }
+ return P
  }
+ return permute(arr, 0, arr.length - 1)
 }
 
-// Driver Code
-const input = [1, 2, 3]
-permutations(input, 0, input.length - 1)
+export { permutations }

Backtracking/tests/GeneratePermutations.test.js

@@ -0,0 +1,14 @@
+import { permutations } from '../GeneratePermutations'
+
+describe('Permutations', () => {
+ it('Permutations of [1, 2, 3]', () => {
+ expect(permutations([1, 2, 3])).toEqual([
+ [ 1, 2, 3 ],
+ [ 1, 3, 2 ],
+ [ 2, 1, 3 ],
+ [ 2, 3, 1 ],
+ [ 3, 1, 2 ],
+ [ 3, 2, 1 ]
+ ])
+ })
+})