# COMBINATION_LOCK The Combination Lock Problem

COMBINATION_LOCK is a MATLAB program which simulates the process of determining the combination of a lock.

This program demonstrates the method of exhaustive search, that is, it searches for an answer by trying every possibility. This requires a way of logically ordering the possibilities.

### Usage:

combination_lock ( m, n, c )
where
• m, the number of dials (perhaps 3).
• n, the number of symbols on each dial (perhaps 10);
• c, a vector of length m, containing the combination, which should be integers in the range 0 to n-1. (perhaps [7,4,9]).

### Languages:

COMBINATION_LOCK is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.

### Related Data and Programs:

BICYCLE_LOCK, a MATLAB library which simulates the process of determining the secret combination of a bicycle lock, an integer between 000 and 999.

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

COMBO, a MATLAB library which includes many combinatorial routines.

PARTITION_PROBLEM, a MATLAB library which seeks solutions of the partition problem, splitting a set of integers into two subsets with equal sum.

SATISFY, a MATLAB program which demonstrates, for a particular circuit, an exhaustive search for solutions of the circuit satisfiability problem.

SUBSET, a MATLAB library which enumerates combinations, partitions, subsets, index sets, and other combinatorial objects.

SUBSET_SUM, a MATLAB library which seeks solutions of the subset sum problem.

TSP_BRUTE, a MATLAB program which reads a file of city-to-city distances and solves the traveling salesperson problem, using brute force.

### Reference:

1. Donald Kreher, Douglas Simpson,
Combinatorial Algorithms,
CRC Press, 1998,
ISBN: 0-8493-3988-X,
LC: QA164.K73.
2. Silvano Martello, Paolo Toth,
Knapsack Problems: Algorithms and Computer Implementations,
Wiley, 1990,
ISBN: 0-471-92420-2,
LC: QA267.7.M37.