From 263693e45cc6665e3c149cdcd4ba05875b8f9004 Mon Sep 17 00:00:00 2001
From: Simon Green <mail@simon.green>
Date: Fri, 14 Jan 2022 15:21:19 +1100
Subject: sgreen solutions to challenge 147

---
 challenge-147/sgreen/python/ch-1.py | 50 +++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100755 challenge-147/sgreen/python/ch-1.py

(limited to 'challenge-147/sgreen/python/ch-1.py')

diff --git a/challenge-147/sgreen/python/ch-1.py b/challenge-147/sgreen/python/ch-1.py
new file mode 100755
index 0000000000..1b77f58482
--- /dev/null
+++ b/challenge-147/sgreen/python/ch-1.py
@@ -0,0 +1,50 @@
+#!/usr/bin/env python
+
+import math
+
+
+def is_prime(number):
+    # Return true or false if the number is a prime
+    if number < 2:
+        return False
+
+    for i in range(2, int(math.sqrt(number)) + 1):
+        if number % i == 0:
+            return False
+
+    # It's a prime
+    return True
+
+
+def is_trunc_prime(number):
+    # Return true or false if the number and all it's left truncated
+    #  parts is a prime. Start with the smallest figure first
+    n = str(number)
+
+    if '0' in n:
+        # A left-truncatable prime cannot contain a zero
+        return False
+
+    for i in range(len(n), 0, -1):
+        if not is_prime(int(n[i - 1:])):
+            return False
+
+    return True
+
+
+def main():
+    solutions = []
+    number = 1
+
+    # Keep increasing number by one until we have twenty truncated prime
+    #  numbers
+    while len(solutions) < 20:
+        if is_trunc_prime(number):
+            solutions.append(number)
+        number += 1
+
+    print(*solutions, sep=', ')
+
+
+if __name__ == '__main__':
+    main()
-- 
cgit