9

solutions/9/README.md

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+# 9
+
+Again the python std lib saved me some lines of code. `itertools` to the rescue and basically we are done.
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>23278925</li>
+    <li>4011064</li>
+  </ol>
+</details>

solutions/9/python/main.py

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+from os.path import join, dirname
+from typing import List, Optional, Set, Tuple
+from itertools import combinations
+
+
+class XMAS:
+
+    def __init__(self, data: str, size: int) -> None:
+        self.size: int = size
+        self.position: int = size
+        self.buffer: List[int] = [
+            int(x)
+            for x in data.strip().split('\n')
+        ]
+
+    def check_next(self) -> bool:
+        possible = [
+            a + b
+            for a, b in combinations(self.buffer[self.position - self.size: self.position], 2)
+        ]
+        return self.buffer[self.position] in possible
+
+    def find_first_invalid(self) -> int:
+        l = len(self.buffer)
+        while self.position < l:
+            valid = self.check_next()
+            if not valid:
+                return self.buffer[self.position]
+            self.position += 1
+        raise Exception
+
+    def find_slice(self, target: int):
+        l = len(self.buffer)
+        for n in range(l):
+            for m in range(n, l):
+                slice = self.buffer[n: m]
+                if sum(slice) == target:
+                    return min(slice) + max(slice)
+        raise Exception
+
+
+data = join(dirname(__file__), '../data.txt')
+with open(data) as f:
+    xmas = XMAS(f.read(), 25)
+
+    first_invalid = xmas.find_first_invalid()
+    print(first_invalid)
+
+    solution = xmas.find_slice(first_invalid)
+    print(solution)