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Commit b0c55ec

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mmapplebecktrekhleb
authored andcommitted
add recursive solution to permutations with repetitions problem (trekhleb#52)
* add recursive solution to permutations with repetitions problem * fix untested function, failing test * add comments
1 parent 8d3f83c commit b0c55ec

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4 files changed

+87
-49
lines changed

4 files changed

+87
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Lines changed: 2 additions & 49 deletions
Original file line numberDiff line numberDiff line change
@@ -1,55 +1,8 @@
11
import permutateWithRepetitions from '../permutateWithRepetitions';
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import testPermutateWithRepetitionsFn from './testPermutateWithRepetitionsFn';
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describe('permutateWithRepetitions', () => {
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it('should permutate string with repetition', () => {
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const permutations0 = permutateWithRepetitions([]);
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expect(permutations0).toEqual([]);
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const permutations1 = permutateWithRepetitions(['A']);
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expect(permutations1).toEqual([
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['A'],
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]);
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const permutations2 = permutateWithRepetitions(['A', 'B']);
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expect(permutations2).toEqual([
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['A', 'A'],
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['A', 'B'],
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['B', 'A'],
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['B', 'B'],
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]);
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const permutations3 = permutateWithRepetitions(['A', 'B', 'C']);
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expect(permutations3).toEqual([
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['A', 'A', 'A'],
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['A', 'A', 'B'],
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['A', 'A', 'C'],
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['A', 'B', 'A'],
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['A', 'B', 'B'],
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['A', 'B', 'C'],
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['A', 'C', 'A'],
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['A', 'C', 'B'],
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['A', 'C', 'C'],
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['B', 'A', 'A'],
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['B', 'A', 'B'],
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['B', 'A', 'C'],
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['B', 'B', 'A'],
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['B', 'B', 'B'],
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['B', 'B', 'C'],
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['B', 'C', 'A'],
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['B', 'C', 'B'],
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['B', 'C', 'C'],
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['C', 'A', 'A'],
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['C', 'A', 'B'],
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['C', 'A', 'C'],
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['C', 'B', 'A'],
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['C', 'B', 'B'],
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['C', 'B', 'C'],
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['C', 'C', 'A'],
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['C', 'C', 'B'],
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['C', 'C', 'C'],
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]);
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const permutations4 = permutateWithRepetitions(['A', 'B', 'C', 'D']);
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expect(permutations4.length).toBe(4 * 4 * 4 * 4);
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testPermutateWithRepetitionsFn(permutateWithRepetitions);
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});
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});
Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
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import permutateWithRepetitionsRecursive from '../permutateWithRepetitionsRecursive';
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import testPermutateWithRepetitionsFn from './testPermutateWithRepetitionsFn';
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describe('permutateWithRepetitionsRecursive', () => {
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it('should permutate string with repetition', () => {
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testPermutateWithRepetitionsFn(permutateWithRepetitionsRecursive);
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});
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});
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Original file line numberDiff line numberDiff line change
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export default function testPermutateWithRepetitionsFn(fn) {
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const permutations0 = fn([]);
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expect(permutations0).toEqual([]);
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const permutations1 = fn(['A']);
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expect(permutations1).toEqual([
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['A'],
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]);
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const permutations2 = fn(['A', 'B']);
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expect(permutations2).toEqual([
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['A', 'A'],
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['A', 'B'],
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['B', 'A'],
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['B', 'B'],
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]);
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const permutations3 = fn(['A', 'B', 'C']);
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expect(permutations3).toEqual([
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['A', 'A', 'A'],
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['A', 'A', 'B'],
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['A', 'A', 'C'],
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['A', 'B', 'A'],
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['A', 'B', 'B'],
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['A', 'B', 'C'],
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['A', 'C', 'A'],
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['A', 'C', 'B'],
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['A', 'C', 'C'],
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['B', 'A', 'A'],
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['B', 'A', 'B'],
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['B', 'A', 'C'],
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['B', 'B', 'A'],
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['B', 'B', 'B'],
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['B', 'B', 'C'],
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['B', 'C', 'A'],
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['B', 'C', 'B'],
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['B', 'C', 'C'],
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['C', 'A', 'A'],
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['C', 'A', 'B'],
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['C', 'A', 'C'],
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['C', 'B', 'A'],
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['C', 'B', 'B'],
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['C', 'B', 'C'],
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['C', 'C', 'A'],
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['C', 'C', 'B'],
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['C', 'C', 'C'],
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]);
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const permutations4 = fn(['A', 'B', 'C', 'D']);
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expect(permutations4.length).toBe(4 * 4 * 4 * 4);
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}
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Original file line numberDiff line numberDiff line change
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/**
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* @param {*[]} permutationOptions
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* @return {*[]}
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*/
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export default function permutateWithRepetitionsRecursive(
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options,
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n = options.length || 0,
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prefix = [],
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perms = [],
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) {
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// If initial options are null or empty then return empty array
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if (!options || !options.length) return [];
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// If no more iterations then add current prefix to perms array
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if (n === 0) {
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perms.push(prefix);
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return perms;
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}
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// Recursively find permutations and store in perms array
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options.forEach((option) => {
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permutateWithRepetitionsRecursive(options, n - 1, prefix.concat([option]), perms);
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});
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return perms;
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}

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