Add functions to extract rows, colums and blocks

src/board.cr

@@ -1,27 +1,50 @@
 
 module Sudoku
 
+  class BoardException < Exception
+  end
+
   class Board
 
-    alias Value = Nil | Int8
-
-    enum State
-      Valid
-      Invalid
-    end
+    alias Value = Nil | Int32
 
+    @grid : Array(Array(Value))
     getter grid
 
-    def initialize(@width : Int8, @height : Int8)
-      @grid = Array(Value).new(@width * @height, nil)
+    def initialize(@size : Int32, @block_size : Int32)
+      raise BoardException.new() unless @size.divisible_by?(@block_size)
+      @grid = Array(Array(Value)).new(@size) { Array(Value).new(@size, nil) }
     end
 
     def put(value : Value, x, y)
-      @grid[y * @width + x] = value
+      @grid[y][x] = value
     end
 
     def get(x, y)
-      @grid[y * @width + x]
+      @grid[y][x]
+    end
+
+    def check_valid(value : Value, x, y)
+
+    end
+
+    def extract_row(y)
+      @grid[y]
+    end
+
+    def extract_column(x)
+      (0..@size - 1).map { |i| get(x, i) }
+    end
+
+    def extract_block(x, y)
+      block_start_x = x - (x % @block_size)
+      block_start_y = y - (y % @block_size)
+
+      (block_start_y..block_start_y + @block_size - 1).map { |j|
+        (block_start_x..block_start_x + @block_size - 1).map { |i|
+          get(i, j)
+        }
+      }
     end
       
   end