[mypy] fix type annotations for all Project Euler problems (#4747)

* [mypy] fix type annotations for problem003/sol1 and problem003/sol3

* [mypy] fix type annotations for project euler problem007/sol2

* [mypy] fix type annotations for project euler problem008/sol2

* [mypy] fix type annotations for project euler problem009/sol1

* [mypy] fix type annotations for project euler problem014/sol1

* [mypy] fix type annotations for project euler problem 025/sol2

* [mypy] fix type annotations for project euler problem026/sol1.py

* [mypy] fix type annotations for project euler problem037/sol1

* [mypy] fix type annotations for project euler problem044/sol1

* [mypy] fix type annotations for project euler problem046/sol1

* [mypy] fix type annotations for project euler problem051/sol1

* [mypy] fix type annotations for project euler problem074/sol2

* [mypy] fix type annotations for project euler problem080/sol1

* [mypy] fix type annotations for project euler problem099/sol1

* [mypy] fix type annotations for project euler problem101/sol1

* [mypy] fix type annotations for project euler problem188/sol1

* [mypy] fix type annotations for project euler problem191/sol1

* [mypy] fix type annotations for project euler problem207/sol1

* [mypy] fix type annotations for project euler problem551/sol1

project_euler/problem_003/sol1.py

@@ -92,8 +92,8 @@ def solution(n: int = 600851475143) -> int:
         return n
     for i in range(3, int(math.sqrt(n)) + 1, 2):
         if n % i == 0:
-            if isprime(n / i):
-                max_number = n / i
+            if isprime(n // i):
+                max_number = n // i
                 break
             elif isprime(i):
                 max_number = i

project_euler/problem_003/sol3.py

@@ -57,7 +57,7 @@ def solution(n: int = 600851475143) -> int:
             i += 1
         ans = i
         while n % i == 0:
-            n = n / i
+            n = n // i
         i += 1
     return int(ans)
 

project_euler/problem_007/sol2.py

@@ -73,7 +73,7 @@ def solution(nth: int = 10001) -> int:
         raise TypeError("Parameter nth must be int or castable to int.") from None
     if nth <= 0:
         raise ValueError("Parameter nth must be greater than or equal to one.")
-    primes = []
+    primes: list[int] = []
     num = 2
     while len(primes) < nth:
         if isprime(num):

project_euler/problem_008/sol2.py

@@ -70,7 +70,9 @@ def solution(n: str = N) -> int:
     """
 
     return max(
-        reduce(lambda x, y: int(x) * int(y), n[i : i + 13]) for i in range(len(n) - 12)
+        # mypy cannot properly interpret reduce
+        int(reduce(lambda x, y: str(int(x) * int(y)), n[i : i + 13]))
+        for i in range(len(n) - 12)
     )
 
 

project_euler/problem_009/sol1.py

@@ -36,6 +36,8 @@ def solution() -> int:
                     if (a ** 2) + (b ** 2) == (c ** 2):
                         return a * b * c
 
+    return -1
+
 
 def solution_fast() -> int:
     """
@@ -55,6 +57,8 @@ def solution_fast() -> int:
             if a < b < c and (a ** 2) + (b ** 2) == (c ** 2):
                 return a * b * c
 
+    return -1
+
 
 def benchmark() -> None:
     """

project_euler/problem_014/sol1.py

@@ -44,7 +44,7 @@ def solution(n: int = 1000000) -> int:
 
         while number > 1:
             if number % 2 == 0:
-                number /= 2
+                number //= 2
                 counter += 1
             else:
                 number = (3 * number) + 1

project_euler/problem_025/sol2.py

@@ -23,9 +23,10 @@ The 12th term, F12, is the first term to contain three digits.
 What is the index of the first term in the Fibonacci sequence to contain 1000
 digits?
 """
+from typing import Generator
 
 
-def fibonacci_generator() -> int:
+def fibonacci_generator() -> Generator[int, None, None]:
     """
     A generator that produces numbers in the Fibonacci sequence
 

project_euler/problem_026/sol1.py

@@ -39,7 +39,7 @@ def solution(numerator: int = 1, digit: int = 1000) -> int:
     longest_list_length = 0
 
     for divide_by_number in range(numerator, digit + 1):
-        has_been_divided = []
+        has_been_divided: list[int] = []
         now_divide = numerator
         for division_cycle in range(1, digit + 1):
             if now_divide in has_been_divided:

project_euler/problem_037/sol1.py

@@ -76,7 +76,7 @@ def compute_truncated_primes(count: int = 11) -> list[int]:
     >>> compute_truncated_primes(11)
     [23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397]
     """
-    list_truncated_primes = []
+    list_truncated_primes: list[int] = []
     num = 13
     while len(list_truncated_primes) != count:
         if validate(num):

project_euler/problem_044/sol1.py

@@ -42,6 +42,8 @@ def solution(limit: int = 5000) -> int:
             if is_pentagonal(a) and is_pentagonal(b):
                 return b
 
+    return -1
+
 
 if __name__ == "__main__":
     print(f"{solution() = }")

project_euler/problem_046/sol1.py

@@ -85,6 +85,8 @@ def compute_nums(n: int) -> list[int]:
             if len(list_nums) == n:
                 return list_nums
 
+    return []
+
 
 def solution() -> int:
     """Return the solution to the problem"""

project_euler/problem_051/sol1.py

@@ -63,12 +63,12 @@ def digit_replacements(number: int) -> list[list[int]]:
     >>> digit_replacements(3112)
     [[3002, 3112, 3222, 3332, 3442, 3552, 3662, 3772, 3882, 3992]]
     """
-    number = str(number)
+    number_str = str(number)
     replacements = []
     digits = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
 
-    for duplicate in Counter(number) - Counter(set(number)):
-        family = [int(number.replace(duplicate, digit)) for digit in digits]
+    for duplicate in Counter(number_str) - Counter(set(number_str)):
+        family = [int(number_str.replace(duplicate, digit)) for digit in digits]
         replacements.append(family)
 
     return replacements
@@ -106,6 +106,8 @@ def solution(family_length: int = 8) -> int:
 
             return min(primes_in_family)
 
+    return -1
+
 
 if __name__ == "__main__":
     print(solution())

project_euler/problem_074/sol2.py

@@ -20,8 +20,8 @@
     counter increases.
 """
 
-factorial_cache = {}
-factorial_sum_cache = {}
+factorial_cache: dict[int, int] = {}
+factorial_sum_cache: dict[int, int] = {}
 
 
 def factorial(a: int) -> int:

project_euler/problem_080/sol1.py

@@ -26,8 +26,8 @@ def solution() -> int:
         sqrt_number = number.sqrt(decimal_context)
         if len(str(sqrt_number)) > 1:
             answer += int(str(sqrt_number)[0])
-            sqrt_number = str(sqrt_number)[2:101]
-            answer += sum(int(x) for x in sqrt_number)
+            sqrt_number_str = str(sqrt_number)[2:101]
+            answer += sum(int(x) for x in sqrt_number_str)
     return answer
 
 
@@ -35,3 +35,4 @@ if __name__ == "__main__":
     import doctest
 
     doctest.testmod()
+    print(f"{solution() = }")

project_euler/problem_099/sol1.py

@@ -22,12 +22,14 @@ def solution(data_file: str = "base_exp.txt") -> int:
     >>> solution()
     709
     """
-    largest = [0, 0]
+    largest: float = 0
+    result = 0
     for i, line in enumerate(open(os.path.join(os.path.dirname(__file__), data_file))):
         a, x = list(map(int, line.split(",")))
-        if x * log10(a) > largest[0]:
-            largest = [x * log10(a), i + 1]
-    return largest[1]
+        if x * log10(a) > largest:
+            largest = x * log10(a)
+            result = i + 1
+    return result
 
 
 if __name__ == "__main__":

project_euler/problem_101/sol1.py

@@ -202,7 +202,7 @@ def solution(func: Callable[[int], int] = question_function, order: int = 10) ->
     ]
 
     ret: int = 0
-    poly: int
+    poly: Callable[[int], int]
     x_val: int
 
     for poly in polynomials:

project_euler/problem_188/sol1.py

@@ -19,7 +19,7 @@ References:
 """
 
 
-# small helper function for modular exponentiation
+# small helper function for modular exponentiation (fast exponentiation algorithm)
 def _modexpt(base: int, exponent: int, modulo_value: int) -> int:
     """
     Returns the modular exponentiation, that is the value
@@ -36,7 +36,7 @@ def _modexpt(base: int, exponent: int, modulo_value: int) -> int:
     if exponent == 1:
         return base
     if exponent % 2 == 0:
-        x = _modexpt(base, exponent / 2, modulo_value) % modulo_value
+        x = _modexpt(base, exponent // 2, modulo_value) % modulo_value
         return (x * x) % modulo_value
     else:
         return (base * _modexpt(base, exponent - 1, modulo_value)) % modulo_value

project_euler/problem_191/sol1.py

@@ -26,7 +26,7 @@ References:
 """
 
 
-cache = {}
+cache: dict[tuple[int, int, int], int] = {}
 
 
 def _calculate(days: int, absent: int, late: int) -> int:

project_euler/problem_207/sol1.py

@@ -90,7 +90,7 @@ def solution(max_proportion: float = 1 / 12345) -> int:
                 perfect_partitions += 1
         if perfect_partitions > 0:
             if perfect_partitions / total_partitions < max_proportion:
-                return partition_candidate
+                return int(partition_candidate)
         integer += 1
 
 

project_euler/problem_551/sol1.py

@@ -12,9 +12,10 @@ You are given a(10^6) = 31054319.
 Find a(10^15)
 """
 
+
 ks = [k for k in range(2, 20 + 1)]
 base = [10 ** k for k in range(ks[-1] + 1)]
-memo = {}
+memo: dict[int, dict[int, list[list[int]]]] = {}
 
 
 def next_term(a_i, k, i, n):