Generate permutations of JavaScript array

Question

I have an array of n different elements in javascript, I know there are n! possible ways to order these elements. I want to know what\'s the most effective (fastest) algorit

Answer 1

This is my version based on le_m's code:

function permute(array) {
	Array.prototype.swap = function (index, otherIndex) {
		var valueAtIndex = this[index]

		this[index] = this[otherIndex]
		this[otherIndex] = valueAtIndex
	}

	var result = [array.slice()]

	, length = array.length

	for (var i = 1, heap = new Array(length).fill(0)
		; i < length
	;)
		if (heap[i] < i) {
			array.swap(i, i % 2 && heap[i])
			result.push(array.slice())
			heap[i]++
			i = 1
		} else {
			heap[i] = 0
			i++
		}

	return result
}

console.log(permute([1, 2, 3]))

This is my recursive JavaScript implementation of the same algorithm:

Array.prototype.swap = function (index, otherIndex) {
	var valueAtIndex = this[index]

	this[index] = this[otherIndex]
	this[otherIndex] = valueAtIndex
}

Array.prototype.permutation = function permutation(array, n) {
	array = array || this
	n = n || array.length

	var result = []

	if (n == 1)
		result = [array.slice()]
	else {
		const nextN = n - 1

		for (var i = 0; i < nextN; i++) {
			result.push(...permutation(array, nextN))
			array.swap(Number(!(n % 2)) && i, nextN)
		}

		result.push(...permutation(array, nextN))
	}

	return result
}

console.log([1, 2, 3].permutation())