30-seconds-of-code/snippets/js/s/merge-sort.md

title, type, language, tags, cover, dateModified

title	type	language	tags	cover	dateModified
Merge sort	snippet	javascript	algorithm array recursion	baloons-field	2020-12-27T22:44:32+02:00

Sorts an array of numbers, using the merge sort algorithm.

• Use recursion.
• If the length of the array is less than 2, return the array.
• Use Math.floor() to calculate the middle point of the array.
• Use Array.prototype.slice() to slice the array in two and recursively call mergeSort() on the created subarrays.
• Finally, use Array.from() and Array.prototype.shift() to combine the two sorted subarrays into one.

const mergeSort = arr => {
  if (arr.length < 2) return arr;
  const mid = Math.floor(arr.length / 2);
  const l = mergeSort(arr.slice(0, mid));
  const r = mergeSort(arr.slice(mid, arr.length));
  return Array.from({ length: l.length + r.length }, () => {
    if (!l.length) return r.shift();
    else if (!r.length) return l.shift();
    else return l[0] > r[0] ? r.shift() : l.shift();
  });
};

mergeSort([5, 1, 4, 2, 3]); // [1, 2, 3, 4, 5]