Initial commit

problem-37.py

@@ -0,0 +1,55 @@
+
+NUM_PRIMES = 11
+START_NUM = 9
+
+
+def is_prime(n):
+    """Returns True if n is prime."""
+    if n == 1:
+        return False
+    if n == 2:
+        return True
+    if n == 3:
+        return True
+    if n % 2 == 0:
+        return False
+    if n % 3 == 0:
+        return False
+
+    i = 5
+    w = 2
+
+    while i * i <= n:
+        if n % i == 0:
+            return False
+        i += w
+        w = 6 - w
+
+    return True
+
+
+def truncatable_prime(i):
+    j = i
+    for _ in range(len(j)):
+        if not is_prime(int(j)):
+            return False
+        j = j[1:]
+    j = i
+    for _ in range(len(j)):
+        if not is_prime(int(j)):
+            return False
+        j = j[:-1]
+    return True
+
+
+if __name__ == '__main__':
+    results = []
+    i = START_NUM
+    while len(results) != NUM_PRIMES:
+        i += 1
+        if truncatable_prime(str(i)):
+            results.append(i)
+
+    print(results)
+    print(sum(results))
+