104 lines
3.6 KiB
Markdown
104 lines
3.6 KiB
Markdown
---
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id: 5a23c84252665b21eecc801d
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title: Split a character string based on change of character
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challengeType: 5
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forumTopicId: 302322
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---
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## Description
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<section id='description'>
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Split a (character) string into comma (plus a blank) delimited strings based on a change of character (left to right).
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Blanks should be treated as any other character (except they are problematic to display clearly). The same applies to commas.
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For instance, the string:
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<pre>
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"gHHH5YY++///\"
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</pre>
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should be split as:
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<pre>
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["g", "HHH", "5", "YY", "++", "///", "\" ];
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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>split</code> should be a function.
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testString: assert(typeof split == 'function', '<code>split</code> should be a function.');
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- text: <code>split("hello")</code> should return an array.
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testString: assert(Array.isArray(split("hello")), '<code>split("hello")</code> should return an array.');
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- text: <code>split("hello")</code> should return <code>["h", "e", "ll", "o"]</code>.
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testString: assert.deepEqual(split("hello"), ["h", "e", "ll", "o"], '<code>split("hello")</code> should return <code>["h", "e", "ll", "o"]</code>.');
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- text: <code>split("commission")</code> should return <code>["c", "o", "mm", "i", "ss", "i", "o", "n"]</code>.
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testString: assert.deepEqual(split("commission"), ["c", "o", "mm", "i", "ss", "i", "o", "n"], '<code>split("commission")</code> should return <code>["c", "o", "mm", "i", "ss", "i", "o", "n"]</code>.');
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- text: <code>split("ssss----====llloooo")</code> should return <code>["ssss", "----", "====", "lll", "oooo"]</code>.
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testString: assert.deepEqual(split("ssss----====llloooo"), ["ssss", "----", "====", "lll", "oooo"], '<code>split("ssss----====llloooo")</code> should return <code>["ssss", "----", "====", "lll", "oooo"]</code>.');
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- text: <code>split("sssmmmaaammmaaat")</code> should return <code>["sss", "mmm", "aaa", "mmm", "aaa", "t"]</code>.
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testString: assert.deepEqual(split("sssmmmaaammmaaat"), ["sss", "mmm", "aaa", "mmm", "aaa", "t"], '<code>split("sssmmmaaammmaaat")</code> should return <code>["sss", "mmm", "aaa", "mmm", "aaa", "t"]</code>.');
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- text: <code>split("gHHH5YY++///\")</code> should return <code>["g", "HHH", "5", "YY", "++", "///", "\\"]</code>.
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testString: assert.deepEqual(split("gHHH5YY++///\\"), ["g", "HHH", "5", "YY", "++", "///", "\\"], '<code>split("gHHH5YY++///\")</code> should return <code>["g", "HHH", "5", "YY", "++", "///", "\\"]</code>.');
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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 split(str) {
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// Good luck!
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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 split(str) {
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const concat = xs =>
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xs.length > 0 ? (() => {
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const unit = typeof xs[0] === 'string' ? '' : [];
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return unit.concat.apply(unit, xs);
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})() : [];
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const group = xs => groupBy((a, b) => a === b, xs);
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const groupBy = (f, xs) => {
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const dct = xs.slice(1)
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.reduce((a, x) => {
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const
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h = a.active.length > 0 ? a.active[0] : undefined,
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blnGroup = h !== undefined && f(h, x);
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return {
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active: blnGroup ? a.active.concat([x]) : [x],
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sofar: blnGroup ? a.sofar : a.sofar.concat([a.active])
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};
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}, {
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active: xs.length > 0 ? [xs[0]] : [],
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sofar: []
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});
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return dct.sofar.concat(dct.active.length > 0 ? [dct.active] : []);
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};
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const map = (f, xs) => xs.map(f);
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const stringChars = s => s.split('');
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return map(concat, group(stringChars(str)))
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}
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```
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</section>
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