ts-math/lib/permute.js

A collection of math functions and packages written in Typescript

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.permute = exports.rotate = exports.fact = void 0;
/**
 * The factorial of n.
 */
function fact(n) {
    var res = 1;
    for (let i = 2; i <= n; i++) {
        res *= i;
    }
    return res;
}
exports.fact = fact;
/**
 * Rotate the elements in array from index n to m. Example [0,1,2,3,4,5], 2,4 => [0,1,4,2,3,5]
 * @param {Array} arr - The array to rotate
 * @param {int} n - Start index
 * @param {int} m - End Index (including)
 */
function rotate(arr, n, m) {
    let s = arr[m];
    for (let i = m - 1; i >= n; i--) {
        arr[i + 1] = arr[i];
    }
    arr[n] = s;
}
exports.rotate = rotate;
/**
 * Permutes an array.
 * @param {*} arr - The array to permute
 * @param {*} idx - The permutation index. An index between 0 and fact(arr.length)-1
 */
function permute(arr, idx) {
    var i = 0;
    var d = fact(arr.length - 1);
    var r = idx;
    var n;
    while (i < arr.length - 1) {
        n = r;
        r %= d;
        n = (n - r) / d;
        rotate(arr, i, i + n);
        i++;
        d /= arr.length - i;
    }
    rotate(arr, i, i + r);
    return arr;
}
exports.permute = permute;
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