Solution to problem 28

src/Python/Problem028.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+"""
+Created on 3 Jan 2020
+
+@author: David Doblas Jiménez
+@email: daviddoji@pm.me
+
+Solution for problem 28 of Project Euler
+https://projecteuler.net/problem=28
+"""
+
+from utils import timeit
+
+
+@timeit("Problem 28")
+def compute():
+    """
+    Starting with the number 1 and moving to the right in a clockwise
+    direction a 5 by 5 spiral is formed as follows:
+
+                                21 22 23 24 25
+                                20  7  8  9 10
+                                19  6  1  2 11
+                                18  5  4  3 12
+                                17 16 15 14 13
+
+    It can be verified that the sum of the numbers on the diagonals is 101.
+
+    What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral
+    formed in the same way?
+    """
+    size = 1001  # Must be odd
+    ans = 1   # Special case for size 1
+    step = 0
+    i, cur = 1, 1
+    while step < size-1:
+        step = i * 2
+        for j in range(1, 5):
+            cur += step
+            ans += cur
+        i += 1
+
+    return ans
+
+
+if __name__ == "__main__":
+
+    print(f"Result for Problem 28: {compute()}")