chopsuey/lib/ChopSuey.js

Combinatorics: subsets, permutations, etc.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.ChopSuey = void 0;
class ChopSuey {
    static *generateSubsets(elements, offset = 0) {
        while (offset < elements.length) {
            const first = elements[offset++];
            for (const subset of this.generateSubsets(elements, offset)) {
                subset.push(first);
                yield subset;
            }
        }
        yield [];
    }
    static *generatePermutations(elements) {
        yield elements.slice();
        const stack = Array(elements.length).fill(0);
        let i = 1;
        while (i < elements.length) {
            if (stack[i] < i) {
                const j = i % 2 && stack[i];
                [elements[i], elements[j]] = [elements[j], elements[i]];
                stack[i]++;
                i = 1;
                yield elements.slice();
            }
            else {
                stack[i] = 0;
                i++;
            }
        }
    }
    static getSubsets(elements) {
        return [...this.generateSubsets(elements)];
    }
    static getPermutations(elements) {
        return [...this.generatePermutations(elements)];
    }
    static getShuffled(elements) {
        const shuffle = (copyElements) => {
            for (let i = copyElements.length - 1; i > 0; i--) {
                const j = Math.floor(Math.random() * (i + 1));
                [copyElements[i], copyElements[j]] = [copyElements[j], copyElements[i]];
            }
        };
        const copy = elements.slice();
        shuffle(copy);
        return copy;
    }
}
exports.ChopSuey = ChopSuey;