Go Sudoku

A very simple learning application for Go.

Background

When learning a new language, I often go for a Sudoku solver application. This is my attempt to put some of my recent Golang knowledge to work.

Run

go build -o output/go-sudoku cmd/go-sudoku/main.go
./output/go-sudoku <file>

or

go run cmd/go-sudoku/main.go <file>

Test

go test ./cmd/go-sudoku/...

Benchmarks

There are a few benchmarks that are useful when making changes to the algorithm.

go test ./cmd/go-sudoku/solver/... -run=^$ -bench ^Benchmark

Algorithm

This section will describe the algorithm used to solve the puzzels. The basic idea is this.

1. Find the possible options for each empty space
2. Examine space-by-space for places with:
   1. Only one possible solution
   2. Only space in the row with a possible solution
   3. Only space in the column with a possible solution
   4. Only space in the cube with a possible solution

Input

The application requires a file path parameter to a puzzle. The puzzle file should be nine lines long. Each line contains a space seperated list of entries. Each entry is either a number if given in the puzzle or a zero (0) to indicate the space is unsolved.

0 3 8 2 0 0 0 4 5
0 1 0 6 0 5 0 0 0
5 0 7 0 8 0 0 0 0
3 0 1 0 6 2 0 7 0
9 0 0 5 0 7 0 0 4
0 4 0 8 3 0 6 0 2
0 0 0 0 2 0 3 0 8
0 0 0 9 0 3 0 2 0
2 7 0 0 0 8 4 9 0