A pawn can move on 10x10 chequerboard horizontally, vertically and diagonally by these rules:

1. 3 tiles moving North (N), West (W), South (S) and East (E)
2. 2 tiles moving NE, SE, SW and NW
3. Moves are only allowed if the ending tile exists on the board
4. Starting from initial position, the pawn can visit each tile only once

1. Solution Approach:

I have Followed the Warnsdorff’s Algorithm approach to solve the problem.

1. Build the 10*10 Board with unvisited(-1)
2. Prepare all possible patterns row_pattern = [3, 2, 0, -2, -3, -2, 0, 2], col_pattern  = [0, -2, -3, -2, 0, 2, 3, 2]
3. Pawn can start from any valid position on the board. 
4. By using the above pattern. get the unvisited(-1) tile with minimal degree from the current position
5. Once find the next position, update the position in board as visited. 
6. Keep continue step 4 and 5 until all the tiles got visited

note: Board is in one dimensional array, Index calculation will be board[col * BOARD_SIZE + row]

2. App setup and run the App: 

 

1. Required ruby 2.5.1
2. unzip the app folder and go to app path.
3. Run bundle install  $ bundle install
4. Run the application with below command. pass the row and col values of the initial position, if no arguments passed  by default 0,0 will be considered.  $ ruby lib/visit.rb 3 2

3. Running Unit test cases:   

   $ rspec spec/pawn_tour_spec.rb