List permutations

permutation.js

(function () {
	"use strict";

	var n = 4, k = 4,

	ret = [];

	{
		let pool = [], queue = [];

		for (let i = 0; i < n; i += 1) {
			pool[i] = i + 1;
			queue.push([pool[i]]);
		}

		while (queue.length > 0) {
			let cur = queue.shift();

			if (cur.length === k) {
				ret.push(cur);
				continue;
			}

			pool.forEach(function (x) {
				if (cur.indexOf(x) === - 1) {
					let toPush = cur.slice(0);
					toPush.push(x);
					queue.push(toPush);
				}
			});
		}
	}

	console.log(ret);
	console.log(ret.length);
})();