feat(learn): add word frequency challenge to rosetta section (#39424)
* feat(learn): add word frequency challenge to rosetta section * Update curriculum/challenges/english/10-coding-interview-prep/rosetta-code/word-frequency.english.md Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com> * Update curriculum/challenges/english/10-coding-interview-prep/rosetta-code/word-frequency.english.md Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com> * Update curriculum/challenges/english/10-coding-interview-prep/rosetta-code/word-frequency.english.md Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com> * Update curriculum/challenges/english/10-coding-interview-prep/rosetta-code/word-frequency.english.md Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com> * Update curriculum/challenges/english/10-coding-interview-prep/rosetta-code/word-frequency.english.md Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com> * Update curriculum/challenges/english/10-coding-interview-prep/rosetta-code/word-frequency.english.md Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com> * fix: tests * fix: revert challenge so it can have multiple solutions * Update curriculum/challenges/english/10-coding-interview-prep/rosetta-code/word-frequency.english.md Co-authored-by: Shaun Hamilton <51722130+Sky020@users.noreply.github.com> Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com> Co-authored-by: Shaun Hamilton <51722130+Sky020@users.noreply.github.com>pull/39474/head
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"594810f028c0303b75339ad3",
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"Vector dot product"
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[
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"5e94a54cc7b022105bf0fd2c",
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"Word frequency"
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---
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id: 5e94a54cc7b022105bf0fd2c
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title: Word frequency
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challengeType: 5
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isHidden: false
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forumTopicId: 393913
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---
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## Description
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<section id='description'>
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Given a text string and an integer n, return the n most common words in the file (and the number of their occurrences) in decreasing frequency.
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</section>
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## Instructions
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<section id='instructions'>
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Write a function to count the occurrences of each word and return the n most commons words along with the number of their occurences in decreasing frequency.
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The function should return a 2D array with each of the elements in the following form: <code>[word, freq]</code>. <code>word</code> should be the lowercase version of the word and <code>freq</code> the number denoting the count.
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The function should return an empty array, if no string is provided.
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The function should be case insensitive, for example, the strings "Hello" and "hello" should be treated the same.
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You can treat words that have special characters such as underscores, dashes, apostrophes, commas, etc., as distinct words.
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For example, given the string "Hello hello goodbye", your function should return <code>[['hello', 2], ['goodbye', 1]]</code>.
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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>wordFrequency</code> should be a function.
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testString: assert(typeof wordFrequency == 'function');
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- text: <code>wordFrequency</code> should return an array.
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testString: assert(Array.isArray(wordFrequency("test")));
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- text: <code>wordFrequency("Hello hello world", 2)</code> should return <code>[['hello', 2], ['world', 1]]</code>
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testString: assert.deepEqual(wordFrequency(example_1, 2), example_1_solution)
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- text: <code>wordFrequency("The quick brown fox jumped over the lazy dog", 1)</code> should return <code>[['the', 2]]</code>
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testString: assert.deepEqual(wordFrequency(example_2, 1), example_2_solution)
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- text: <code>wordFrequency("Opensource opensource open-source open source", 1)</code> should return <code>[['opensource', 2]]</code>
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testString: assert.deepEqual(wordFrequency(example_3, 1), example_3_solution)
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- text: <code>wordFrequency("Apple App apply aPP aPPlE", 3)</code> should return <code>[['app', 2], ['apple', 2], ['apply', 1]]</code> or <code>[['apple', 2], ['app', 2], ['apply', 1]]</code>
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testString: const arr = JSON.stringify(wordFrequency(example_4, 3)); assert(arr === example_4_solution_a || arr === example_4_solution_b)
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- text: <code>wordFrequency("c d a d c a b d d c", 4)</code> should return <code>[['d', 4], ['c', 3], ['a', 2], ['b', 1]]</code>
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testString: assert.deepEqual(wordFrequency(example_5, 4), example_5_solution)
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- text: <code>wordFrequency("", 5)</code> should return <code>[]</code>
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testString: assert.deepEqual(wordFrequency(example_6, 5), example_6_solution)
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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 wordFrequency(txt, n) {
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// Good luck!
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}
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```
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</div>
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### Before Test
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<div id='js-setup'>
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```js
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var example_1 = 'Hello hello world';
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var example_1_solution = [['hello', 2], ['world', 1]];
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var example_2 = 'The quick brown fox jumped over the lazy dog';
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var example_2_solution = [['the', 2]];
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var example_3 = 'Opensource opensource open-source open source';
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var example_3_solution = [['opensource', 2]];
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var example_4 = 'Apple App apply aPP aPPlE';
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var example_4_solution_a = "[[\"app\",2],[\"apple\",2],[\"apply\",1]]";
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var example_4_solution_b = "[[\"apple\",2],[\"app\",2],[\"apply\",1]]";
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var example_5 = 'c d a d c a b d d c';
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var example_5_solution = [['d', 4], ['c', 3], ['a', 2], ['b', 1]];
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var example_6 = '';
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var example_6_solution = [];
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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 wordFrequency(txt, n) {
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var words = txt.split(/\s+/);
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var wordCount = {};
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words.forEach(word => {
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if (word == '') {
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return;
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}
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const lowerWord = word.toLowerCase();
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wordCount[lowerWord] =
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lowerWord in wordCount ? wordCount[lowerWord] + 1 : 1;
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});
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var wordsArray = [];
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for (let [word, count] of Object.entries(wordCount)) {
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wordsArray.push([word, count]);
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}
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wordsArray.sort((a, b) => {
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if (a[1] !== b[1]) {
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return b[1] - a[1];
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} else if (a[0] !== b[0]) {
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return a[0] < b[0] ? -1 : 1;
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}
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return 0;
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});
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return wordsArray.slice(0, n);
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}
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```
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</section>
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