aureooms/js-permutation

/**
 * Computes the sequence of transpositions that if applied to
 * <code>sigma</code> result in <code>invert(sigma)</code>. Needs an helper
 * array to keep track of processed elements. See {@link itranspositions} for
 * higher level API.
 *
 * @param {Array} sigma Input permutation.
 * @param {Array} used Helper array.
 * @return {IterableIterator} Iterator over the transpositions.
 */
export function* _itranspositions(sigma, used) {
    for (const s of sigma) {
        if (used[s]) continue;

        used[s] = true;

        let image = sigma[s];

        while (image !== s) {
            used[image] = true;

            yield [s, image];

            image = sigma[image];
        }
    }
}