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

Author: pikulet

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__":