Fix import of utils

src/project_euler_python/create_template.py

@@ -22,7 +22,7 @@ def create_problem():
                                     https://projecteuler.net/problem={args["problem"]}
                                     """
 
-                                    from utils import timeit
+                                    from project_euler_python.utils import timeit
 
 
                                     @timeit("Problem {(args["problem"]):0>3}")

src/project_euler_python/problems_001_050/Problem022.py

@@ -34,7 +34,7 @@ def compute():
         names = sorted(f.read().replace('"', "").split(","))
 
     ans = 0
-    for idx, name in enumerate(names, 1):
+    for idx, name in enumerate(names, start=1):
         ans += sum(ord(char) - 64 for char in name) * idx
 
     return ans

src/project_euler_python/problems_001_050/Problem023.py

@@ -9,9 +9,21 @@ Solution for problem 023 of Project Euler
 https://projecteuler.net/problem=23
 """
 
+from itertools import combinations_with_replacement
+
 from project_euler_python.utils import timeit
 
 
+def _get_abundant_numbers(limit):
+    divisor_sums = [0 for _ in range(limit)]
+
+    for divisor in range(1, limit):
+        for multiple in range(divisor * 2, limit, divisor):
+            divisor_sums[multiple] += divisor
+
+    return [number for number in range(1, limit) if divisor_sums[number] > number]
+
+
 @timeit("Problem 023")
 def compute():
     """
@@ -35,25 +47,19 @@ def compute():
     sum of two abundant numbers.
     """
 
-    limit = 28124
-    divisor_sum = [0] * limit
-    for i in range(1, limit):
-        for j in range(i * 2, limit, i):
-            divisor_sum[j] += i
+    limit = 28123 + 1
+    abundant_numbers = _get_abundant_numbers(limit)
 
-    abundant_nums = [i for (i, x) in enumerate(divisor_sum) if x > i]
+    expressible_sums = {
+        first + second
+        for first, second in combinations_with_replacement(
+            abundant_numbers,
+            2,
+        )
+        if first + second < limit
+    }
 
-    expressible = [False] * limit
-    for i in abundant_nums:
-        for j in abundant_nums:
-            if i + j < limit:
-                expressible[i + j] = True
-            else:
-                break
-
-    ans = sum(i for (i, x) in enumerate(expressible) if not x)
-
-    return ans
+    return sum(number for number in range(1, limit) if number not in expressible_sums)
 
 
 if __name__ == "__main__":

src/project_euler_python/problems_001_050/Problem024.py

@@ -9,7 +9,7 @@ Solution for problem 024 of Project Euler
 https://projecteuler.net/problem=24
 """
 
-from itertools import permutations
+from itertools import islice, permutations
 
 from project_euler_python.utils import timeit
 
@@ -28,9 +28,10 @@ def compute():
     0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?
     """
 
+    limit = 1_000_000
     digits = list(range(10))
-    _permutations = list(permutations(digits))
-    ans = "".join(str(digit) for digit in _permutations[999_999])
+    millionth_permutation = next(islice(permutations(digits), limit - 1, limit))
+    ans = "".join(str(digit) for digit in millionth_permutation)
 
     return ans
 

src/project_euler_python/problems_001_050/Problem026.py

@@ -37,11 +37,17 @@ def compute():
 
     cycle_length = 0
     ans = 0
+    # Because denominators with factor 2 contribute only to the terminating
+    # part of a decimal. The repeating behavior comes from the part of the
+    # denominator that is coprime with 10, so evens are skipped
     for number in range(3, 1000, 2):
         if number % 5 == 0:
             continue
         p = 1
-        while 10**p % number != 1:
+        remainder = 10 % number
+        while remainder != 1:
+            # avoid huge exponentiation
+            remainder = (remainder * 10) % number
             p += 1
         if p > cycle_length:
             cycle_length, ans = p, number