2016: d07: ex1: add solution

2016/d07/ex1/ex1.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+
+import sys
+
+
+def solve(input: str) -> int:
+    def has_abba(input: str) -> bool:
+        for i in range(4, len(input) + 1):
+            a, b, c, d = (input[i - j] for j in range(4, 0, -1))
+            if a == b:
+                continue
+            if a != d:
+                continue
+            if b != c:
+                continue
+            return True
+        return False
+
+    def supports_tls(address: str) -> bool:
+        abba_found = False
+        is_hypernet = False
+        i = 0
+        while i < len(address):
+            if is_hypernet:
+                j = address.find("]", i)
+            else:
+                j = address.find("[", i)
+            if j == -1:
+                j = len(address)
+            if has_abba(address[i:j]):
+                if is_hypernet:
+                    return False
+                abba_found = True
+            i = j
+            is_hypernet = not is_hypernet
+        return abba_found
+
+    return sum(map(supports_tls, input.splitlines()))
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()