Rewrite challenge #1 in Python + code optimizations

Author: Mauricio Klein

challenge-1/Gemfile

@@ -0,0 +1,4 @@
+test:
+	python test_*.py
+
+.PHONY: test

challenge-1/Gemfile.lock

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+RIGHT = 1
+DOWN  = 2
+LEFT  = 3
+UP    = 4
+
+#
+# Time  complexity: O(n*m)
+# Space complexity: O(n*m) (result array)
+#
+def spiral_traverse(arr, n_rows, m_columns):
+  def inbounds(row, column):
+    return (0 <= row < n_rows) and (0 <= column < m_columns)
+
+  matrix = to_matrix(arr, n_rows, m_columns)
+  result = []
+
+  row, column, direction = 0, 0, RIGHT
+
+  for _ in range(n_rows * m_columns):
+    # Visit the cell
+    result.append(matrix[row][column])
+    matrix[row][column] = None
+
+    # Check if we need to change directions
+    nr, nc = next_step(direction, row, column)
+    if not inbounds(nr, nc) or matrix[nr][nc] == None:
+      direction = next_direction(direction)
+
+    row, column = next_step(direction, row, column)
+
+  return result
+
+def next_step(direction, row, column):
+  return {
+    RIGHT: (row    , column + 1),
+    DOWN : (row + 1, column    ),
+    LEFT : (row    , column - 1),
+    UP   : (row - 1, column    )
+  }[direction]
+
+def next_direction(current_direction):
+  return {
+    RIGHT: DOWN,
+    DOWN : LEFT,
+    LEFT : UP,
+    UP   : RIGHT
+  }[current_direction]
+
+def to_matrix(arr, rows, columns):
+  matrix = [ [ 0 for i in range(columns) ] for j in range(rows) ]
+
+  for i in range(columns):
+    for j in range(rows):
+      matrix[i][j] = arr[i * rows + j]
+
+  return matrix

challenge-1/Makefile

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+import unittest
+from solver import spiral_traverse
+
+class TestSolver(unittest.TestCase):
+  def test_spiral_traverse(self):
+    arr =      [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
+    expected = [1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10]
+    rows, columns = 4, 4
+
+    self.assertEqual(spiral_traverse(arr, rows, columns), expected)
+
+if __name__ == "__main__":
+    unittest.main()