127 lines
3.9 KiB
Markdown
127 lines
3.9 KiB
Markdown
---
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id: 5a23c84252665b21eecc8017
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title: Soundex
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challengeType: 5
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forumTopicId: 302320
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---
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## Description
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<section id='description'>
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Soundex is an algorithm for creating indices for words based on their pronunciation.
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The goal is for homophones to be encoded to the same representation so that they can be matched despite minor differences in spelling (from <a href="https://en.wikipedia.org/wiki/soundex" target="_blank">the WP article</a>).
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There is a major issue in many of the implementations concerning the separation of two consonants that have the same soundex code! According to the <a href="https://www.archives.gov/research/census/soundex.html" target="_blank">official Rules</a>. So check for instance if <b>Ashcraft</b> is coded to <b>A-261</b>.
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<ul>
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<li>If a vowel (A, E, I, O, U) separates two consonants that have the same soundex code, the consonant to the right of the vowel is coded. Tymczak is coded as T-522 (T, 5 for the M, 2 for the C, Z ignored (see "Side-by-Side" rule above), 2 for the K). Since the vowel "A" separates the Z and K, the K is coded.</li>
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<li>If "H" or "W" separate two consonants that have the same soundex code, the consonant to the right of the vowel is not coded. Example: Ashcraft is coded A-261 (A, 2 for the S, C ignored, 6 for the R, 1 for the F). It is not coded A-226.</li>
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</ul>
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</section>
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## Instructions
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<section id='instructions'>
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Write a function that takes a string as a parameter and returns the encoded string.
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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>soundex</code> should be a function.
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testString: assert(typeof soundex == 'function');
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- text: <code>soundex("Soundex")</code> should return a string.
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testString: assert(typeof soundex("Soundex") == 'string');
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- text: <code>soundex("Soundex")</code> should return <code>"S532"</code>.
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testString: assert.equal(soundex("Soundex"), "S532");
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- text: <code>soundex("Example")</code> should return <code>"E251"</code>.
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testString: assert.equal(soundex("Example"), "E251");
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- text: <code>soundex("Sownteks")</code> should return <code>"S532"</code>.
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testString: assert.equal(soundex("Sownteks"), "S532");
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- text: <code>soundex("Ekzampul")</code> should return <code>"E251"</code>.
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testString: assert.equal(soundex("Ekzampul"), "E251");
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- text: <code>soundex("Euler")</code> should return <code>"E460"</code>.
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testString: assert.equal(soundex("Euler"), "E460");
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- text: <code>soundex("Gauss")</code> should return <code>"G200"</code>.
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testString: assert.equal(soundex("Gauss"), "G200");
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- text: <code>soundex("Hilbert")</code> should return <code>"H416"</code>.
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testString: assert.equal(soundex("Hilbert"), "H416");
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- text: <code>soundex("Knuth")</code> should return <code>"K530"</code>.
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testString: assert.equal(soundex("Knuth"), "K530");
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- text: <code>soundex("Lloyd")</code> should return <code>"L300"</code>.
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testString: assert.equal(soundex("Lloyd"), "L300");
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- text: <code>soundex("Lukasiewicz")</code> should return <code>"L222"</code>.
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testString: assert.equal(soundex("Lukasiewicz"), "L222");
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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 soundex(s) {
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}
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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 soundex(s) {
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var a = s.toLowerCase().split('');
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var f = a.shift(),
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r = '',
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codes = {
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a: '',
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e: '',
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i: '',
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o: '',
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u: '',
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b: 1,
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f: 1,
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p: 1,
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v: 1,
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c: 2,
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g: 2,
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j: 2,
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k: 2,
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q: 2,
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s: 2,
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x: 2,
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z: 2,
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d: 3,
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t: 3,
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l: 4,
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m: 5,
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n: 5,
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r: 6
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};
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r =
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f +
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a
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.map(function(v, i, a) {
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return codes[v];
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})
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.filter(function(v, i, a) {
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return i === 0 ? v !== codes[f] : v !== a[i - 1];
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})
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.join('');
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return (r + '000').slice(0, 4).toUpperCase();
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}
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```
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</section>
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