Sudoku Solver
Name: Alseny Diallo
Email: Alsenidiallo@pcc.edu
4/15/2015 ...... initial creation date

Description:
  Sudoku puzzle solver that uses backtracking.
  Before backtracking the program attempts to 
  reduce the search space by solving for some 
  of the numbers by located "naked singles" as 
  described at 
      http://www.sudokuwiki.org/Naked_Candidates
  For more on the backtracking algorithm see the
  following video:
      https://youtu.be/p-gpaIGRCQI

Building
  The source is in written in C++11 and requires
  a C++ compiler of recent vintage (g++ 4.7 or later,
  clang++). The provided Makefile will automate
  the build via "make" (use -O3 in CXXFLAGS for best performace).

         make         # builds 'solvesudoku' app
         make clean   # deletes build riffraff

Running:
  The program reads a 81 character string from stdin
  that describes the input puzzle in row-major order.
  Each character in the string is either a dot '.' or
  a digit for an empty space or initial number respectively.
  I have include two files 'simple.txt' and 'hard.txt'
  which contain a variety of sample puzzles.
  For example, to run the program using the 13th puzzle
  from "hard.txt", do the following:

        sed -n "13p" hard.txt | ./solvesudoku 

  The program will "pretty print" the original puzzle,
  puzzle with deduced numbers, and then the final
  solved puzzle. Puzzles should take no more than 30 sec
  to solve on a machine of recent vintage.

  To solve all the problems in 'hard.txt' you can use
  the provided Perl script:

       ./solve.pl hard.txt

GitLab Continuous Integration (CI)
 
   There is a .gitlab-ci.yml provided for trigger CI on
   git push to gitlab server. This runs the scripts in the
   t/ directory using a (modern) gcc environment.

Files in archive:

README.txt ........... This file
Makefile ............. make builds solvesudoku app
SudokuGrid.h ......... SudokuGrid class definition
simple.txt ........... Some "simple" sudoku puzzles
hard.txt ............. Some "hard" sudoku puzzles
solve.pl ............. inputs a battery of puzzles at solver
solvesudoku.cpp ...... solver source cide
sudokucheck.pl........ verifies and checks solution   
testpuzzles.txt ...... Test puzzles used in CI
.gitlab-ci.yml ....... CI test specification for GitLab
.gitignore ........... files for git to ignore
t/00-readme.t ........ Test script for README
t/01-build.t ......... Test script for building code
t/02-run.t ........... Test script for runtime