28 lines
962 B
Markdown
28 lines
962 B
Markdown
---
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title: Stable sort
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tags: array
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cover: horse-sunset
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firstSeen: 2018-02-06T18:33:49+02:00
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lastUpdated: 2020-10-22T20:24:30+03:00
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---
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Performs stable sorting of an array, preserving the initial indexes of items when their values are the same.
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- Use `Array.prototype.map()` to pair each element of the input array with its corresponding index.
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- Use `Array.prototype.sort()` and a `compare` function to sort the list, preserving their initial order if the items compared are equal.
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- Use `Array.prototype.map()` to convert back to the initial array items.
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- Does not mutate the original array, but returns a new array instead.
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```js
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const stableSort = (arr, compare) =>
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arr
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.map((item, index) => ({ item, index }))
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.sort((a, b) => compare(a.item, b.item) || a.index - b.index)
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.map(({ item }) => item);
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```
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```js
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const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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const stable = stableSort(arr, () => 0); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
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```
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