sgreen solutions to challenge 147

1 files changed, 32 insertions, 0 deletions

diff --git a/challenge-147/sgreen/python/ch-2.py b/challenge-147/sgreen/python/ch-2.py
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+++ b/challenge-147/sgreen/python/ch-2.py
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+#!/usr/bin/env python
+
+import math
+
+
+def pentagon_number(n):
+    return int(n * (3 * n - 1) / 2)
+
+
+def is_pentagon_number(x):
+    n = math.sqrt(24 * x + 1) + 1
+    return int(n / 6) if n % 6 == 0 else None
+
+
+def main():
+    n1 = 2
+    while True:
+        p1 = pentagon_number(n1)
+        for n2 in range(1, n1):
+            p2 = pentagon_number(n2)
+
+            s1 = is_pentagon_number(p1 + p2)
+            s2 = is_pentagon_number(p1 - p2)
+
+            if s1 is not None and s2 is not None:
+                print(f'P({n1}) + P({n2}) = {p1} + {p2} = { p1 + p2 } = P({s1})')
+                print(f'P({n1}) - P({n2}) = {p1} - {p2} = { p1 - p2 } = P({s2})')
+                return
+        n1 += 1
+
+
+main()