# combo

combo, a MATLAB code which includes routines for ranking, unranking, enumerating and randomly selecting balanced sequences, cycles, graphs, Gray codes, subsets, partitions, permutations, restricted growth functions, Pruefer codes and trees.

Routines are available to count, list, rank and unrank such objects

• BAL, balanced sequences;
• CYCLE, permutations of the first N integers in cycle form;
• GRAPH, graphs stored as a list of edges.
• GRAY, Gray codes;
• KNAPSACK, optimally filling a knapsack of given size using a set of smaller objects;
• KSUBSET, subsets of size exactly K from a set of N objects;
• NPART, partitions of an integer having exactly N parts;
• PART, partitions of an integer;
• PERM, permutations of the first N integers in standard form;
• PRUEFER, Pruefer codes;
• RGF, restricted growth functions;
• SETPART, partitions of a set;
• SUBSET, subsets of a set of N objects;
• TABLEAU, tableaus;
• TREE, trees;

Some of these sets of objects can be ordered in several different ways, and in some cases, a separate set of ranking, unranking, and successor routines are available for the various orderings (lexical, colexical, revolving door, Trotter-Johnson).

Kreher and Stinson provide C source-code for the routines, as well as other information, at their web site.

### Languages:

combo is available in a C version and a C++ version and a Fortran90 version and a MATLAB version and an Octave version and a Python version.

### Related Data and Programs:

change_making, a MATLAB code which considers the change making problem, in which a given sum is to be formed using coins of various denominations.

combination_lock, a MATLAB code which simulates the process of determining the secret combination of a lock.

floyd, a MATLAB code which implements floyd's algorithm for finding the shortest distance between pairs of nodes on a directed graph.

gray_code_display, a MATLAB code which computes the Hamming distance tables for both the binary and gray codes, and displays 3d plots that illustrate how the gray code does a better job of providing nearby representations for nearby numbers.

monomial, a MATLAB code which enumerates, lists, ranks, unranks and randomizes multivariate monomials in a space of m dimensions, with total degree less than n, equal to n, or lying within a given range.

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polynomial, a MATLAB code which adds, multiplies, differentiates, evaluates and prints multivariate polynomials in a space of m dimensions.

set_theory, a MATLAB code which demonstrates MATLAB commands that implement various set theoretic operations.

subset, a MATLAB code which generates, ranks and unranks various combinatorial objects.

subset_sum, a MATLAB code which seeks solutions of the subset sum problem.

toms515, a MATLAB code which can select subsets of size k from a set of size n. this is a version of acm toms algorithm 515, by bill buckles, matthew lybanon.

unicycle, a MATLAB code which considers permutations containing a single cycle, sometimes called cyclic permutations.

### Reference:

1. Donald Kreher, Douglas Simpson,
Combinatorial Algorithms,
CRC Press, 1998,
ISBN: 0-8493-3988-X,
LC: QA164.K73.

### Source Code:

Last revised on 11 September 2022. <%-- John Burkardt -->