ldm-partition/index.js

Largest differencing method

"use strict";
// Based on https://en.wikipedia.org/wiki/Largest_differencing_method
Object.defineProperty(exports, "__esModule", { value: true });
function partition(items, k = 2, getWeight = (x) => Number(x)) {
    const jobs = [...items].map((x) => [[x], ...[...Array(k - 1)].map(() => [])]);
    while (jobs.length > 1) {
        const [a, b] = select2(jobs, getWeight);
        const [jobA, jobB] = [jobs[a], jobs[b]];
        const merged = jobA.map((l, i) => [...l, ...jobB[jobB.length - 1 - i]]);
        const cache = new Map();
        merged.forEach((list) => cache.set(list, weigh(list, getWeight)));
        merged.sort((l1, l2) => { var _a, _b; return ((_a = cache.get(l2)) !== null && _a !== void 0 ? _a : 0) - ((_b = cache.get(l1)) !== null && _b !== void 0 ? _b : 0); });
        jobs[a] = merged;
        jobs.splice(b, 1);
    }
    return jobs.length == 0 ? [...Array(k)].map(() => []) : jobs[0];
}
exports.default = partition;
function select2(buckets, getWeight) {
    const diffs = buckets.map((it) => measureDiff(it, getWeight));
    const max1 = Math.max(...diffs);
    const a = diffs.indexOf(max1);
    diffs[a] = -Infinity;
    const max2 = Math.max(...diffs);
    const b = diffs.indexOf(max2);
    return [a, b];
}
function measureDiff(bucket, getWeight) {
    const max = weigh(bucket[0], getWeight);
    const min = weigh(bucket[bucket.length - 1], getWeight);
    return max - min;
}
function weigh(list, getWeight) {
    return list.reduce((sum, it) => sum + getWeight(it), 0);
}
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