@toruslabs/metadata-helpers/dist/lib.cjs/helpers/math.js

Helper methods for metadata

'use strict';

var stringify = require('json-stable-stringify');

/**
 * Return the element that appears at least `t` times in `arr`,
 * or undefined if no element meets the threshold.
 * Comparison uses JSON-stable-stringify for deep equality.
 */
const thresholdSame = (arr, t) => {
  const hashMap = {};
  for (let i = 0; i < arr.length; i += 1) {
    const str = stringify(arr[i]);
    hashMap[str] = hashMap[str] ? hashMap[str] + 1 : 1;
    if (hashMap[str] === t) {
      return arr[i];
    }
  }
  return undefined;
};
/**
 * Generate all k-combinations of a set.
 * @param s - Array of numbers, or a number n (shorthand for [0..n-1]).
 * @param k - Size of each combination.
 */
const kCombinations = (s, k) => {
  let set = s;
  if (typeof set === "number") {
    set = Array.from({
      length: set
    }, (_, i) => i);
  }
  if (k > set.length || k <= 0) {
    return [];
  }
  if (k === set.length) {
    return [set];
  }
  if (k === 1) {
    return set.reduce((acc, cur) => [...acc, [cur]], []);
  }
  const combs = [];
  let tailCombs = [];
  for (let i = 0; i <= set.length - k + 1; i += 1) {
    tailCombs = kCombinations(set.slice(i + 1), k - 1);
    for (let j = 0; j < tailCombs.length; j += 1) {
      combs.push([set[i], ...tailCombs[j]]);
    }
  }
  return combs;
};
/**
 * Calculate the median of a numeric array.
 * Returns 0 for empty arrays.
 */
function calculateMedian(arr) {
  const arrSize = arr.length;
  if (arrSize === 0) return 0;
  const sortedArr = [...arr].sort((a, b) => a - b);
  if (arrSize % 2 !== 0) {
    return sortedArr[Math.floor(arrSize / 2)];
  }
  const mid1 = sortedArr[arrSize / 2 - 1];
  const mid2 = sortedArr[arrSize / 2];
  return (mid1 + mid2) / 2;
}

exports.calculateMedian = calculateMedian;
exports.kCombinations = kCombinations;
exports.thresholdSame = thresholdSame;