codev0 / js-combinatorics

A javascript combinatorics library, currently a function that generates combinations of an array's elements

js-combinatorics

A javascript combinatorics library. Right now, it provides just the following utility:

combinatorics.processCombinations(array, process, minCombLen, maxCombLen)

A generator of combinations of an array's elements

• It's fast (0.2 secs for an array of length 20)
• It's able to compute only some subsets of combinations (using minCombLen and maxCombLen)
• It's memory-constant, because it doesn't build an array with the combinations (it receives a processing function instead, which can build an array if it needs to). Furthermore, the function can return false to halt mid-process.

Usage examples:

var deck = []; // A standard deck of cards
for(var i = 1; i <= 52; i++) deck.push(i); // Deck initialization, [1..52]

// Let's calculate how many unique first hands there are (it should be 2,598,960)
var count = 0,
	sdate = new Date();
combinatorics.processCombinations(deck, function(combination){count += 1;}, 5, 5);
// Notice that I'm simply counting, but I could be processing the combinations in any other way
console.log(count + ' combinations processed in ' + (new Date() - sdate)/1000 + ' seconds');
>> 2598960 combinations processed in 0.371 seconds

// Given a hand and the opportunity to discard from 1 to 5 of the cards, let's calculate how many
// different outcomes there can be (it should be 1,729,647, +1 if you count the option of not discarding)
count = 0;
sdate = new Date();
combinatorics.processCombinations(deck.slice(5), function(combination){count += 1;}, 1, 5);
// Notice that I'm simply counting, but I could be processing the combinations in any other way
console.log(count + ' combinations processed in ' + (new Date() - sdate)/1000 + ' seconds');
>> 1729647 combinations processed in 0.232 seconds

// A simple example
combinatorics.processCombinations([1,2,3,4], function(combination){console.log(combination)});
>> [1]
>> [2]
>> [3]
>> [4]
>> [1, 2]
>> [1, 3]
>> [1, 4]
>> [2, 3]
>> [2, 4]
>> [3, 4]
>> [1, 2, 3]
>> [1, 2, 4]
>> [1, 3, 4]
>> [2, 3, 4]
>> [1, 2, 3, 4]