109 lines
2.6 KiB
Markdown
109 lines
2.6 KiB
Markdown
---
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title: Combinations
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id: 5958469238c0d8d2632f46db
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challengeType: 5
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forumTopicId: 302233
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---
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## Description
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<section id='description'>
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Given non-negative integers <code>m</code> and <code>n</code>, generate all size <code>m</code> combinations of the integers from <code>0</code> (zero) to <code>n-1</code> in sorted order (each combination is sorted and the entire table is sorted).
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<strong>Example:</strong>
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<code>3</code> comb <code>5</code> is:
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<pre>
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0 1 2
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0 1 3
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0 1 4
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0 2 3
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0 2 4
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0 3 4
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1 2 3
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1 2 4
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1 3 4
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2 3 4
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</pre>
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>combinations</code> is a function.
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testString: assert(typeof combinations === 'function');
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- text: <code>combinations(3, 5)</code> should return <code>[[0, 1, 2], [0, 1, 3], [0, 1, 4], [0, 2, 3], [0, 2, 4], [0, 3, 4], [1, 2, 3], [1, 2, 4], [1, 3, 4], [2, 3, 4]]</code>.
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testString: assert.deepEqual(combinations(testInput1[0], testInput1[1]), testOutput1);
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- text: <code>combinations(4, 6)</code> should return <code>[[0,1,2,3], [0,1,2,4], [0,1,2,5], [0,1,3,4], [0,1,3,5], [0,1,4,5], [0,2,3,4], [0,2,3,5], [0,2,4,5], [0,3,4,5], [1,2,3,4], [1,2,3,5], [1,2,4,5], [1,3,4,5], [2,3,4,5]]</code>
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testString: assert.deepEqual(combinations(testInput2[0], testInput2[1]), testOutput2);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function combinations(m, n) {
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// Good luck!
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return true;
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}
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```
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</div>
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### After Test
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<div id='js-teardown'>
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```js
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const testInput1 = [3, 5];
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const testOutput1 = [[0, 1, 2], [0, 1, 3], [0, 1, 4], [0, 2, 3], [0, 2, 4], [0, 3, 4], [1, 2, 3], [1, 2, 4], [1, 3, 4], [2, 3, 4]];
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const testInput2 = [4, 6];
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const testOutput2 = [[0, 1, 2, 3], [0, 1, 2, 4], [0, 1, 2, 5], [0, 1, 3, 4], [0, 1, 3, 5], [0, 1, 4, 5], [0, 2, 3, 4], [0, 2, 3, 5], [0, 2, 4, 5], [0, 3, 4, 5], [1, 2, 3, 4], [1, 2, 3, 5], [1, 2, 4, 5], [1, 3, 4, 5], [2, 3, 4, 5]];
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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function combinations(m, n) {
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const nArr = [...Array(n).keys()];
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return (function generateCombinations (size, numArr) {
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const ret = [];
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for (let i = 0; i < numArr.length; i++) {
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if (size === 1) {
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ret.push([numArr[i]]);
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}
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else {
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const sub = generateCombinations(size - 1, numArr.slice(i + 1, numArr.length));
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for (let subI = 0; subI < sub.length; subI++) {
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const next = sub[subI];
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next.unshift(numArr[i]);
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ret.push(next);
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}
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}
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}
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return ret;
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}(m, nArr));
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}
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```
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</section>
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