permutation-sjt/dist/index.d.ts

A quite fast non-recursive permutation algorithm, Steinhaus–Johnson–Trotter algorithm (Even's speedup)

/**
 * Steinhaus–Johnson–Trotter algorithm, Even's speedup
 * https://en.wikipedia.org/wiki/Steinhaus%E2%80%93Johnson%E2%80%93Trotter_algorithm
 *
 *
 * The Steinhaus–Johnson–Trotter algorithm or Johnson–Trotter algorithm generates
 * all of the permutations of n elements. Each permutation in the sequence that
 * it generates differs from the previous permutation by swapping two adjacent
 * elements of the sequence.
 *
 * An improvement of the Steinhaus–Johnson–Trotter algorithm by Shimon Even
 * provides an improvement to the running time
 * of the algorithm by storing additional information for each element in the
 * permutation: its position, and a direction (positive, negative, or zero) in which
 * it is currently moving.
 */
export declare class Permutation {
    private n;
    private start;
    private numbers;
    private directions;
    private positions;
    private terminated;
    /**
     *
     * @param n numbers in the arrray 1..n
     */
    constructor(n: number, start?: number);
    /**
     * Checks if there is a permutation to return.
     *
     * @returns
     */
    hasNext(): boolean;
    /**
     * Returns the next permutation of the Steinhaus–Johnson–Trotter algorithm,
     * starting with [1,2,3, ..., n].
     *
     * Returns undefined if the permutations have been exhausted.
     *
     * @returns the next permutation or undefined
     */
    next(): number[];
    /**
     * At each step, the algorithm finds the greatest element with a nonzero direction,
     * and swaps it in the indicated direction.
     *
     * When all numbers become unmarked, the algorithm terminates.
     */
    private generateNext;
    private swapWithNextElementInDirection;
}