How to implement cartesian product of n array with different lenghts in javascript?

Question

let's say that i have the following array:

data[size] = Array('s', 'm');
data[color] = Array('blue', 'red');

I need a function that outputs me the following array

variations[] = Array('s', 'blue');
variations[] = Array('s', 'red');
variations[] = Array('m', 'blue');
variations[] = Array('m', 'red');

The function must work also on arrays like:

data[size] = Array('s', 'm', 'l');
data[color] = Array('blue', 'red');
data[version] = Array('run', 'walk');

It should give an array like

variations[] = Array('s', 'blue', 'run');
variations[] = Array('s', 'blue', 'walk');
variations[] = Array('s', 'red', 'run');
variations[] = Array('s', 'red', 'walk');

And so on ...

How can i implement it?

p.s.: if there is a specific name for this problem let me know so i'll edit the question title for future use

How you implement it begins with showing some effort at implementing it yourself — Dexygen, Sep 25 '14 at 14:26
"How can I loop over two arrays and add their elements to a different array" is your starting point. Go and learn about loops. — Andy, Sep 25 '14 at 14:28
do you want a simple implementation?for example two cases .data lenght = 2 or 3 as input? — Giannis Grivas, Sep 25 '14 at 14:29
thanks Hunter McMillen; what i need is an implementation of a function that can return as an array the Cartesian Product of n arrays with different lenghts — Scalax, Sep 25 '14 at 14:47

Enrique Carro · Accepted Answer · 2014-09-25T15:45:03.770

The following works having n arrays:

function cartesianProduct(data) {

    var current = [[]];
    for (var p in data) {
        var arr = data[p];
        var newCurrent = [];
        for (var c = 0; c < current.length; c++) {
            var baseArray = current[c];
            for (var a = 0; a < arr.length; a++) {
                var clone = baseArray.slice();
                clone.push(arr[a]);
                newCurrent.push(clone);
            }
        }
        current = newCurrent;
    }

    return current;
}

for the following data:

var data = {
    size: ['s', 'm'],
    color: ['blue', 'red'],
    version: ['run', 'walk', 'jump']
};

will return all the combinations:

var variations = [
    ["s","blue","run"],
    ["s","blue","walk"],
    ["s","blue","jump"],
    ["s","red","run"],
    ["s","red","walk"],
    ["s","red","jump"],
    ["m","blue","run"],
    ["m","blue","walk"],
    ["m","blue","jump"],
    ["m","red","run"],
    ["m","red","walk"],
    ["m","red","jump"]
];

thank you Enrique! This perfectly solved my problem! – Scalax Sep 25 '14 at 17:02 — Scalax, Sep 25 '14 at 17:02

score 0 · Answer 2 · answered Sep 25 '14 at 14:28

Your syntax is no valid JS, it seems PHP.

I assume you have

var data = {
    size: ['s', 'm'],
    color: ['blue', 'red']
};

And you want

var variations = [
    ['s', 'blue'],
    ['s', 'red'],
    ['m', 'blue'],
    ['m', 'red']
];

To get that, you can use

var variations = [];
for (var i=0; i<data.size.length; ++i)
    for (var j=0; j<data.color.length; ++j)
        variations.push([data.size[i], data.color[j]]);

Hotted24 · Answer 3 · 2014-09-25T14:41:13.767

Tried something fancy, working on local :

var variations = []
var str = "";
var ind = 0;
index = [];

for (var k in data)
{
    index[index.length] = k;
    str+="for(var i"+ind+" in data["+k+"])";
    ind++;
}
str += "{variations[variations.length] = [";
for (;ind >= 0; ind--)
{
    str+="data["+index[ind]+"][i"+ind+"]";
    if (ind > 0) str += ",";
    else str+="];";
}
str+= "}";

eval(str);

This allows to have any number of arrays in data =)

How to implement cartesian product of n array with different lenghts in javascript?

3 Answers3

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