1 files changed, 50 insertions, 0 deletions
diff --git a/challenge-159/roger-bell-west/python/ch-1.py b/challenge-159/roger-bell-west/python/ch-1.py
new file mode 100755
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+++ b/challenge-159/roger-bell-west/python/ch-1.py
@@ -0,0 +1,50 @@
+#! /usr/bin/python3
+
+import unittest
+
+from math import gcd
+from functools import reduce
+
+def lcm(m,n):
+  return m//gcd(m,n)*n
+
+def lcmseries(s):
+  return reduce(lcm, s)
+
+def farey(n):
+  l=lcmseries(range(2,n+1))
+  d=dict()
+  s=[]
+  for i in range(1,n+1):
+    m=l // i
+    for j in range(0,i+1):
+      k=m*j
+      if not k in d:
+        d[k]=[j,i]
+        s.append(k)
+  s.sort()
+  return [d[i] for i in s]
+
+class TestFarey(unittest.TestCase):
+
+        def test_ex1(self):
+          self.assertEqual(farey(5),
+                           [[0,1], [1,5], [1,4], [1,3], [2,5], [1,2],
+                            [3,5], [2,3], [3,4], [4,5], [1,1]],
+                           'example 1')
+
+        def test_ex2(self):
+          self.assertEqual(farey(7),
+                           [[0,1], [1,7], [1,6], [1,5], [1,4], [2,7],
+                            [1,3], [2,5], [3,7], [1,2], [4,7], [3,5],
+                            [2,3], [5,7], [3,4], [4,5], [5,6], [6,7],
+                            [1,1]],
+                           'example 2')
+
+        def test_ex3(self):
+          self.assertEqual(farey(4),
+                           [[0,1], [1,4], [1,3], [1,2], [2,3], [3,4],
+                            [1,1]],
+                           'example 3')
+
+unittest.main()