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Combinatorics.xs  view on Meta::CPAN

    return k;
}


/**
 * The only algorithms I have found by now are either recursive, or a
 * naive wrapper around permutations() that loops over all of them and
 * discards the ones with fixed-points.
 *
 * We take here a mixed-approach, which consists on starting with the
 * algorithm in __next_permutation() and tweak a couple of places that
 * allow us to skip a significant number of permutations sometimes.
 *
 * Benchmarking shows this subroutine makes derangements() more than
 * two and a half times faster than permutations() for n = 8.
 */
int __next_derangement(SV* tuple_avptr)
{
    AV* tuple = GETAV(tuple_avptr);
    I32 max_n, min_j, j, h, k;

Combinatorics.xs  view on Meta::CPAN

            adjust = 1 - n;
            SETIV(odometer, i, adjust);
        }
    }

    return (AV*) sv_2mortal((SV*) subset);
}

/** -------------------------------------------------------------------
 *
 * XS stuff starts here.
 *
 */

MODULE = Algorithm::Combinatorics   PACKAGE = Algorithm::Combinatorics
PROTOTYPES: DISABLE

int
__next_combination(tuple_avptr, max_n)
    SV* tuple_avptr
    int max_n