93 lines
1.8 KiB
Markdown
93 lines
1.8 KiB
Markdown
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---
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title: Averages/Mode
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id: 594d8d0ab97724821379b1e6
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challengeType: 5
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forumTopicId: 302226
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---
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## Description
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<section id='description'>
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Write a program to find the <a href='https://en.wikipedia.org/wiki/Mode (statistics)' title='wp: Mode (statistics)' target='_blank'>mode</a> value of a collection.
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The case where the collection is empty may be ignored. Care must be taken to handle the case where the mode is non-unique.
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If it is not appropriate or possible to support a general collection, use a vector (array), if possible. If it is not appropriate or possible to support an unspecified value type, use integers.
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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>mode</code> should be a function.
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testString: assert(typeof mode === 'function');
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- text: <code>mode([1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17])</code> should equal <code>[6]</code>
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testString: assert.deepEqual(mode(arr1), [6]);
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- text: <code>mode([1, 2, 4, 4, 1])</code> should equal <code>[1, 4]</code>.
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testString: assert.deepEqual(mode(arr2).sort(), [1, 4]);
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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 mode(arr) {
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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 arr1 = [1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17];
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const arr2 = [1, 2, 4, 4, 1];
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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 mode(arr) {
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const counter = {};
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let result = [];
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let max = 0;
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// for (const i in arr) {
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arr.forEach(el => {
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if (!(el in counter)) {
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counter[el] = 0;
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}
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counter[el]++;
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if (counter[el] === max) {
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result.push(el);
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}
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else if (counter[el] > max) {
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max = counter[el];
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result = [el];
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}
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});
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return result;
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}
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```
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</section>
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