Find all possible subset combos in an array?

javascript arrays subset
Stephen Belanger picture Stephen Belanger · Apr 22, 2011 · Viewed 39.5k times · Source

I need to get all possible subsets of an array with a minimum of 2 items and an unknown maximum. Anyone that can help me out a bit?

Say I have the following array:

[1, 2, 3]

How do I get this?

[
    [1, 2],
    [1, 3],
    [2, 3],
    [1, 2, 3]
]

Answer

Anurag picture Anurag · Apr 22, 2011

After stealing this JavaScript combination generator, I added a parameter to supply the minimum length resulting in,

var combine = function(a, min) {
    var fn = function(n, src, got, all) {
        if (n == 0) {
            if (got.length > 0) {
                all[all.length] = got;
            }
            return;
        }
        for (var j = 0; j < src.length; j++) {
            fn(n - 1, src.slice(j + 1), got.concat([src[j]]), all);
        }
        return;
    }
    var all = [];
    for (var i = min; i < a.length; i++) {
        fn(i, a, [], all);
    }
    all.push(a);
    return all;
}

To use, supply an array, and the minimum subset length desired,

var subsets = combine([1, 2, 3], 2);

Output is,

[[1, 2], [1, 3], [2, 3], [1, 2, 3]]

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