From e1ace4a36aa903411b6b623107e6d8d375bd252c Mon Sep 17 00:00:00 2001
From: Shlomi Fish <shlomif@shlomifish.org>
Date: Mon, 16 Oct 2017 21:08:06 +0300
Subject: [PATCH] Add a faster version of Euler #97.

It finishes in less than 0.1 seconds on my Core i3 machine with both the
on-pypy python2.7 and python3.

Based on:

https://github.com/shlomif/project-euler/tree/master/project-euler/97

Does not require gmpy.
---
 097/non-mersenne-faster.py | 62 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 097/non-mersenne-faster.py

diff --git a/097/non-mersenne-faster.py b/097/non-mersenne-faster.py
new file mode 100644
index 0000000..3c08dd5
--- /dev/null
+++ b/097/non-mersenne-faster.py
@@ -0,0 +1,62 @@
+#!/usr/bin/env python
+
+from six import print_
+
+MOD = 10000000000
+
+
+def get_power_modulo(b, e):
+    if e == 0:
+        return 1
+
+    rec_p = get_power_modulo(b, (e >> 1))
+
+    ret = rec_p * rec_p
+
+    if e & 0x1 != 0:
+        ret *= b
+
+    return ret % MOD
+
+
+def print_pow(b, e, msg):
+    result = get_power_modulo(b, e)
+    print_("%s : %d ** %d %% MOD = %d" % (msg, b, e, result))
+
+print_pow(2, 5,  "2 ** 5 is right.")
+
+print_pow(3, 3, "3 ** 3 is right.")
+
+print_pow(2, 10, "2 ** 10 == 1024 is right.")
+
+print_("Answer = ",
+       ((get_power_modulo(2, 7830457) * 28433 + 1) % MOD))
+
+# Based on:
+# https://github.com/shlomif/project-euler/tree/master/project-euler/97
+#
+# Under the Expat licence.
+#
+# Copyright 2017 Shlomi Fish
+#
+# Permission is hereby granted, free of charge, to any person
+# obtaining a copy of this software and associated documentation
+# files (the "Software"), to deal in the Software without
+# restriction, including without limitation the rights to use,
+# copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following
+# conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+# --------------------------------------------------------------------------