1 files changed, 41 insertions, 0 deletions
diff --git a/challenge-281/roger-bell-west/python/ch-2.py b/challenge-281/roger-bell-west/python/ch-2.py
new file mode 100755
index 0000000000..e6bbe85da8
--- /dev/null
+++ b/challenge-281/roger-bell-west/python/ch-2.py
@@ -0,0 +1,41 @@
+#! /usr/bin/python3
+
+from collections import deque
+
+def cs2xy(a):
+  x = ord(a[0]) - ord('a')
+  y = ord(a[1]) - ord('1')
+  return [x, y]
+
+def knightsmove(ffrom, to):
+  fc = cs2xy(ffrom)
+  tc = cs2xy(to)
+  queue = deque()
+  queue.append((fc[0], fc[1], 0))
+  seen = set()
+  while len(queue) > 0:
+    cc = queue.popleft()
+    if cc[0] == tc[0] and cc[1] == tc[1]:
+      return cc[2]
+    else:
+      for offset in ( (2, 1), (1, 2), (2, -1), (1, -2), (-2, 1), (-1, 2), (-2, -1), (-1, -2) ):
+        x = cc[0] + offset[0]
+        y = cc[1] + offset[1]
+        if x >= 0 and x <= 7 and y >= 0 and y <= 7:
+          cv = x * 8 + y
+          if cv not in seen:
+            queue.append((x, y, cc[2] + 1))
+            seen.add(cv)
+  return -1
+
+import unittest
+
+class TestKnightsmove(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(knightsmove("g2", "a8"), 4, 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(knightsmove("g2", "h2"), 3, 'example 2')
+
+unittest.main()