[рони]

<pre>
<script>
const randomNetto = length => {
    let n = length, ar = [n], sum = n, k = n;
    for (let i = 2; i < length; i++) {
            n *= --k;
            n /= i;
            sum += n;
            ar.push(sum);
            }
    ar = ar.map(a => a / sum);
    return random => {
        let len = 0;
        for (let k of ar) {
            len++;
            if (random < k) break;
        }
        return len
    }
}

function splitSet(set) {
    const random = a => Math.trunc(Math.random() * a),
        sort = (a, b) => a - b;
    let {length} = set = set.slice(0),
    ar = [],
    count = randomNetto(length),
    n = count(Math.random());
    for (let i = 0; i < n; i++) {
        let k = random(length - i);
        ar.push(...set.splice(k, 1))
    }
    ar.sort(sort);
    return ar[0] == 1 ? [ar, set] : [set, ar];
}
let obj = {};
for (let i = 0; i < 63000; i++) {
    let [s1, s2] = splitSet([1, 2, 3, 4, 5, 6, 7])
    obj[[s1]] = (obj[[s1]] >> 0) + 1;
    obj[[s2]] = (obj[[s2]] >> 0) + 1;
}

document.write(JSON.stringify(obj, "", " "))
obj = {};
for (let i = 0; i < 15500; i++) {
    let [s1, s2] = splitSet([1, 2, 3, 4, 5])
    obj[[s1]] = (obj[[s1]] >> 0) + 1;
    obj[[s2]] = (obj[[s2]] >> 0) + 1;
}

document.write(JSON.stringify(obj, "", " "))
</script>
</pre>