|
1 | | -/* |
2 | | - @see: https://stackoverflow.com/a/127898/7794070 |
3 | | - |
4 | | - Lets say your array of letters looks like this: "ABCDEFGH". |
5 | | - You have three indices (i, j, k) indicating which letters you |
6 | | - are going to use for the current word, You start with: |
7 | | - |
8 | | - A B C D E F G H |
9 | | - ^ ^ ^ |
10 | | - i j k |
11 | | - |
12 | | - First you vary k, so the next step looks like that: |
13 | | - |
14 | | - A B C D E F G H |
15 | | - ^ ^ ^ |
16 | | - i j k |
17 | | - |
18 | | - If you reached the end you go on and vary j and then k again. |
19 | | - |
20 | | - A B C D E F G H |
21 | | - ^ ^ ^ |
22 | | - i j k |
| 1 | +/** |
| 2 | + * @param {*[]} comboOptions |
| 3 | + * @param {number} comboLength |
| 4 | + * @param {*[][]} combos |
| 5 | + * @param {*[]} currentCombo |
| 6 | + * @return {*[]} |
| 7 | + */ |
| 8 | +function combineRecursively(comboOptions, comboLength, combos = [], currentCombo = []) { |
| 9 | + if (comboLength === 0) { |
| 10 | + combos.push(currentCombo); |
23 | 11 |
|
24 | | - A B C D E F G H |
25 | | - ^ ^ ^ |
26 | | - i j k |
| 12 | + return combos; |
| 13 | + } |
27 | 14 |
|
28 | | - Once you j reached G you start also to vary i. |
| 15 | + for (let letterIndex = 0; letterIndex <= (comboOptions.length - comboLength); letterIndex += 1) { |
| 16 | + const letter = comboOptions[letterIndex]; |
| 17 | + const restCombinationOptions = comboOptions.slice(letterIndex + 1); |
29 | 18 |
|
30 | | - A B C D E F G H |
31 | | - ^ ^ ^ |
32 | | - i j k |
| 19 | + combineRecursively( |
| 20 | + restCombinationOptions, |
| 21 | + comboLength - 1, |
| 22 | + combos, |
| 23 | + currentCombo.concat([letter]), |
| 24 | + ); |
| 25 | + } |
33 | 26 |
|
34 | | - A B C D E F G H |
35 | | - ^ ^ ^ |
36 | | - i j k |
37 | | - ... |
38 | | - */ |
| 27 | + return combos; |
| 28 | +} |
39 | 29 |
|
40 | 30 | /** |
41 | 31 | * @param {*[]} combinationOptions |
42 | 32 | * @param {number} combinationLength |
43 | 33 | * @return {*[]} |
44 | 34 | */ |
45 | 35 | export default function combineWithoutRepetitions(combinationOptions, combinationLength) { |
46 | | - // If combination length is just 1 then return combinationOptions. |
47 | | - if (combinationLength === 1) { |
48 | | - return combinationOptions.map(option => [option]); |
49 | | - } |
50 | | - |
51 | | - // Init combinations array. |
52 | | - const combinations = []; |
53 | | - |
54 | | - for (let i = 0; i <= (combinationOptions.length - combinationLength); i += 1) { |
55 | | - const smallerCombinations = combineWithoutRepetitions( |
56 | | - combinationOptions.slice(i + 1), |
57 | | - combinationLength - 1, |
58 | | - ); |
59 | | - |
60 | | - for (let j = 0; j < smallerCombinations.length; j += 1) { |
61 | | - const combination = [combinationOptions[i]].concat(smallerCombinations[j]); |
62 | | - combinations.push(combination); |
63 | | - } |
64 | | - } |
65 | | - |
66 | | - // Return all calculated combinations. |
67 | | - return combinations; |
| 36 | + return combineRecursively(combinationOptions, combinationLength); |
68 | 37 | } |
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