Quick sort
JavaScript, Algorithm, Array, Recursion · Oct 13, 2021
Sorts an array of numbers, using the quicksort algorithm.
- Use recursion.
- Use the spread operator (
...) to clone the original array,arr. - If the
lengthof the array is less than2, return the cloned array. - Use
Math.floor()to calculate the index of the pivot element. - Use
Array.prototype.reduce()andArray.prototype.push()to split the array into two subarrays. The first one contains elements smaller than or equal topivotand the second on elements greater than it. Destructure the result into two arrays. - Recursively call
quickSort()on the created subarrays.
const quickSort = arr => {
const a = [...arr];
if (a.length < 2) return a;
const pivotIndex = Math.floor(arr.length / 2);
const pivot = a[pivotIndex];
const [lo, hi] = a.reduce(
(acc, val, i) => {
if (val < pivot || (val === pivot && i != pivotIndex)) {
acc[0].push(val);
} else if (val > pivot) {
acc[1].push(val);
}
return acc;
},
[[], []]
);
return [...quickSort(lo), pivot, ...quickSort(hi)];
};quickSort([1, 6, 1, 5, 3, 2, 1, 4]); // [1, 1, 1, 2, 3, 4, 5, 6]
