mathjs/lib/esm/function/set/setPowerset.js

import { flatten } from '../../utils/array.js';
import { factory } from '../../utils/factory.js';
var name = 'setPowerset';
var dependencies = ['typed', 'size', 'subset', 'compareNatural', 'Index'];
export var createSetPowerset = /* #__PURE__ */factory(name, dependencies, (_ref) => {
  var {
    typed,
    size,
    subset,
    compareNatural,
    Index
  } = _ref;

  /**
   * Create the powerset of a (multi)set. (The powerset contains very possible subsets of a (multi)set.)
   * A multi-dimension array will be converted to a single-dimension array before the operation.
   *
   * Syntax:
   *
   *    math.setPowerset(set)
   *
   * Examples:
   *
   *    math.setPowerset([1, 2, 3])        // returns [[], [1], [2], [3], [1, 2], [1, 3], [2, 3], [1, 2, 3]]
   *
   * See also:
   *
   *    setCartesian
   *
   * @param {Array | Matrix}    a  A (multi)set
   * @return {Array}    The powerset of the (multi)set
   */
  return typed(name, {
    'Array | Matrix': function ArrayMatrix(a) {
      if (subset(size(a), new Index(0)) === 0) {
        // if empty, return empty
        return [];
      }

      var b = flatten(Array.isArray(a) ? a : a.toArray()).sort(compareNatural);
      var result = [];
      var number = 0;

      while (number.toString(2).length <= b.length) {
        result.push(_subset(b, number.toString(2).split('').reverse()));
        number++;
      } // can not return a matrix, because of the different size of the subarrays


      return _sort(result);
    }
  }); // create subset

  function _subset(array, bitarray) {
    var result = [];

    for (var i = 0; i < bitarray.length; i++) {
      if (bitarray[i] === '1') {
        result.push(array[i]);
      }
    }

    return result;
  } // sort subsests by length


  function _sort(array) {
    var temp = [];

    for (var i = array.length - 1; i > 0; i--) {
      for (var j = 0; j < i; j++) {
        if (array[j].length > array[j + 1].length) {
          temp = array[j];
          array[j] = array[j + 1];
          array[j + 1] = temp;
        }
      }
    }

    return array;
  }
});