@handy-common-utils/misc-utils/dist/array.js

Miscellaneous utilities

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.downSampleRandomly = exports.distributeRoundRobin = void 0;
/**
 * Distributes an array into a number of groups in a round robin fashion.
 * This function has been tuned for performance.
 * @param array The input array
 * @param groups Number of groups the elements in the input array need to be distributed into.
 * @returns The result as an array of arrays which each represents a group
 */
function distributeRoundRobin(array, groups) {
    if (groups <= 0) {
        return [];
    }
    // eslint-disable-next-line unicorn/no-new-array
    const result = new Array(groups);
    let remainingElements = array.length;
    for (let groupIndex = 0, remainingGroups = groups; groupIndex < groups; groupIndex++, remainingGroups--) {
        const size = Math.ceil(remainingElements / remainingGroups);
        // eslint-disable-next-line unicorn/no-new-array
        const group = new Array(size);
        result[groupIndex] = group;
        for (let i = 0, j = groupIndex; i < size; i++, j += groups) {
            group[i] = array[j];
        }
        remainingElements -= size;
    }
    return result;
}
exports.distributeRoundRobin = distributeRoundRobin;
// export function distributeRoundRobinWithoutOptimisation<T>(array: Array<T>, groups: number): Array<Array<T>> {
//   if (groups <= 0) {
//     return [];
//   }
//   const result: Array<Array<T>> = [];
//   for (let i = 0; i < groups; i++) {
//     result.push([]);
//   }
//   // eslint-disable-next-line unicorn/no-for-loop
//   for (let i = 0; i < array.length; i++) {
//     result[i % groups].push(array[i]);
//   }
//   return result;
// }
/**
 * Down samples the input array randomly.
 * @param array The input array
 * @param numSamples Number of samples to be taken from the input array.
 *                  If the number of samples is greater than or equal to the length of the input array,
 *                  the output array will contain all the elements in the input array.
 * @param probabilityTransformerFunction A function that turns a random number within [0, 1) to another number within [0, 1).
 *                If not provided, the identity function F(x) = x will be used.
 *                The probability of an element being selected from the input array is determined by this function.
 * @returns A new array with the down sampled elements from the input array.
 *          The order of the elements in the output array is the same as the input array.
 */
function downSampleRandomly(array, numSamples, probabilityTransformerFunction = x => x) {
    if (numSamples <= 0) {
        return [];
    }
    if (numSamples >= array.length) {
        return [...array];
    }
    const result = [];
    const indexes = new Set();
    while (indexes.size < numSamples) {
        const r = Math.random();
        indexes.add(Math.floor(probabilityTransformerFunction(r) * array.length));
    }
    // eslint-disable-next-line unicorn/no-for-loop
    for (let i = 0; i < array.length; i++) {
        if (indexes.has(i)) {
            result.push(array[i]);
        }
    }
    return result;
}
exports.downSampleRandomly = downSampleRandomly;