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Haskell-inspired quick sort in ES6
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quicksort :: (Ord a) => [a] -> [a] | |
quicksort [] = [] | |
quicksort (x:xs) = | |
let smallerSorted = quicksort (filter (<=x) xs) | |
biggerSorted = quicksort (filter (>x) xs) | |
in smallerSorted ++ [x] ++ biggerSorted |
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/* | |
1) passing array | |
> quicksort([4,3,2,1]); // => [1,2,3,4] | |
*/ | |
function quicksort(tail) { | |
if (tail.length === 0) return []; | |
let head = tail.splice(0, 1)[0]; | |
return quicksort(tail.filter( _ => _ <= head)) | |
.concat([head]) | |
.concat(quicksort(tail.filter( _ => _ > head ))) | |
} | |
/* | |
2) via arguments | |
> quicksort(4,3,2,1); // => [1,2,3,4] | |
or: | |
> quicksort(...[4,3,2,1]); // => [1,2,3,4] | |
*/ | |
function quicksort(x, ...xs) { | |
if (arguments.length === 0) return []; | |
return quicksort(...xs.filter( _ => _ <= x)) | |
.concat([x]) | |
.concat(quicksort(...xs.filter( _ => _ > x ))) | |
} |
I like this one :)
const quicksort = array => { if (array.length === 0) return []; let [x, ...xs] = array; return [ ...quicksort(xs.filter(y => y < x)), x, ...quicksort(xs.filter(y => y >= x)) ]; };
One issue is performance since you are filtering the same array twice
function quickSort(values = []) {
const [pivot, ...restValues] = values;
if (!pivot) return [];
if (!restValues.length) return [pivot];
const [lesser, greater] = restValues.reduce((partitions, val) => {
partitions[+(val > pivot)].push(val);
return partitions;
}, [[], []]);
return [
...quickSort(lesser),
pivot,
...quickSort(greater),
];
}
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@AntoineMurat
In your
qsort
"pattern matching" lookalike -You could use default arguments to your advantage -
In
qsortnd
, you calltail.filter
twice per element in the array resulting in many wasted cycles. Usingreduce
we can collapse the two loops into just one -Both
qsort
andqsortnd
can overflow the stack for large arrays. Can you think of a way around this? (Hint: it can still be recursive! and fast!)