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92 lines
2.3 KiB
Markdown
92 lines
2.3 KiB
Markdown
---
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id: 6a0dcd03ee4e68698080ef68
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title: "Challenge 304: Itinerary Arrangements"
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challengeType: 28
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dashedName: challenge-304
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---
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# --description--
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Given an array of at least two optional stops for a day trip, return the number of valid itinerary arrangements.
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The itinerary always includes `"breakfast"`, `"lunch"`, and `"dinner"`, these will not be passed in as arguments. The optional stops can be placed anywhere in the itinerary, subject to the following rules:
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- `"breakfast"` is always first, with at least one stop before `"lunch"`.
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- `"lunch"` must appear before `"dinner"`, with at least one stop in between.
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- At most, one optional stop may appear after `"dinner"`.
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Return the number of valid arrangements.
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# --hints--
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`getItineraryCount(["library", "park"])` should return `2`.
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```js
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assert.equal(getItineraryCount(["library", "park"]), 2);
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```
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`getItineraryCount(["library", "park", "arcade"])` should return `18`.
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```js
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assert.equal(getItineraryCount(["library", "park", "arcade"]), 18);
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```
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`getItineraryCount(["library", "park", "arcade", "store"])` should return `120`.
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```js
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assert.equal(getItineraryCount(["library", "park", "arcade", "store"]), 120);
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```
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`getItineraryCount(["library", "park", "arcade", "store", "cafe"])` should return `840`.
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```js
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assert.equal(getItineraryCount(["library", "park", "arcade", "store", "cafe"]), 840);
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```
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`getItineraryCount(["library", "park", "arcade", "store", "cafe", "market", "museum"])` should return `55440`.
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```js
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assert.equal(getItineraryCount(["library", "park", "arcade", "store", "cafe", "market", "museum"]), 55440);
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```
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# --seed--
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## --seed-contents--
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```js
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function getItineraryCount(stops) {
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return stops;
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}
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```
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# --solutions--
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```js
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function getItineraryCount(stops) {
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const items = ["lunch", "dinner", ...stops];
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let count = 0;
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function permute(arr) {
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if (arr.length === 0) return [[]];
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return arr.flatMap((item, i) =>
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permute([...arr.slice(0, i), ...arr.slice(i + 1)]).map(p => [item, ...p])
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);
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}
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for (const perm of permute(items)) {
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const lunchIdx = perm.indexOf("lunch");
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const dinnerIdx = perm.indexOf("dinner");
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if (lunchIdx >= dinnerIdx) continue;
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if (lunchIdx < 1) continue;
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if (dinnerIdx - lunchIdx < 2) continue;
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if (perm.length - dinnerIdx - 1 > 1) continue;
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count++;
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}
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return count;
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}
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```
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