From 4418292dc4ccd3cae4c414263900351d644a0496 Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Sat, 23 Jan 2021 22:34:58 +0100
Subject: [PATCH] Implement 2019 day 8

---
 2019/aoc2019/__main__.py |  4 ++--
 2019/aoc2019/day06.py    |  2 +-
 2019/aoc2019/day07.py    |  8 ++++----
 2019/aoc2019/day08.py    | 33 +++++++++++++++++++++++++++++++++
 2019/aoc2019/intcode.py  |  9 +++------
 2019/requirements.txt    |  1 +
 6 files changed, 44 insertions(+), 13 deletions(-)
 create mode 100644 2019/aoc2019/day08.py

diff --git a/2019/aoc2019/__main__.py b/2019/aoc2019/__main__.py
index 50b3aec..91147cf 100644
--- a/2019/aoc2019/__main__.py
+++ b/2019/aoc2019/__main__.py
@@ -15,9 +15,9 @@ def main() -> None:
         day = importlib.import_module(f'.day{args.day:02d}', __package__)
 
         if args.part2:
-            function = day.part2
+            function = day.part2  # type: ignore
         else:
-            function = day.part1
+            function = day.part1  # type: ignore
 
         print(function(args.input))
 
diff --git a/2019/aoc2019/day06.py b/2019/aoc2019/day06.py
index f35a7aa..b06601b 100644
--- a/2019/aoc2019/day06.py
+++ b/2019/aoc2019/day06.py
@@ -1,6 +1,6 @@
 from typing import TextIO
 
-import networkx
+import networkx  # type: ignore
 
 
 def read_graph(data: TextIO) -> networkx.DiGraph:
diff --git a/2019/aoc2019/day07.py b/2019/aoc2019/day07.py
index b923273..ff24b5a 100644
--- a/2019/aoc2019/day07.py
+++ b/2019/aoc2019/day07.py
@@ -4,8 +4,8 @@ from typing import List, TextIO, Tuple
 from aoc2019.intcode import read_program, Computer
 
 
-def amplify(phases: Tuple[int], program: List[int]) -> int:
-    amps = []
+def amplify(phases: Tuple[int, ...], program: List[int]) -> int:
+    amps: List[Computer] = []
 
     for i, phase in enumerate(phases):
         amp = Computer(program.copy())
@@ -25,8 +25,8 @@ def amplify(phases: Tuple[int], program: List[int]) -> int:
     return amps[-1].output.pop()
 
 
-def reamplify(phases: Tuple[int], program: List[int]) -> int:
-    amps = []
+def reamplify(phases: Tuple[int, ...], program: List[int]) -> int:
+    amps: List[Computer] = []
 
     for i, _ in enumerate(phases):
         amp = Computer(program.copy())
diff --git a/2019/aoc2019/day08.py b/2019/aoc2019/day08.py
new file mode 100644
index 0000000..8511313
--- /dev/null
+++ b/2019/aoc2019/day08.py
@@ -0,0 +1,33 @@
+from collections import Counter
+from typing import Iterable, TextIO
+
+import numpy  # type: ignore
+
+
+def parse_layers(width: int, height: int, data: TextIO) -> Iterable[numpy.array]:
+    chunk_size = width * height
+
+    content = next(data).strip()
+
+    for pos in range(0, len(content), chunk_size):
+        yield numpy.array([int(c) for c in content[pos:pos + chunk_size]])
+
+
+def part1(data: TextIO) -> int:
+    best_layer: Counter[int] = min((Counter(layer) for layer in parse_layers(25, 6, data)), key=lambda c: c[0])
+
+    return best_layer[1] * best_layer[2]
+
+
+def format_row(row: Iterable[int]) -> str:
+    return ''.join('#' if p == 1 else ' ' for p in row)
+
+
+def part2(data: TextIO) -> str:
+    layers = list(parse_layers(25, 6, data))
+    background = numpy.zeros(25 * 6, numpy.int8)
+
+    for layer in reversed(layers):
+        background[layer != 2] = layer[layer != 2]
+
+    return '\n'.join(format_row(row) for row in background.reshape(6, 25))
diff --git a/2019/aoc2019/intcode.py b/2019/aoc2019/intcode.py
index 206fef4..406b28d 100644
--- a/2019/aoc2019/intcode.py
+++ b/2019/aoc2019/intcode.py
@@ -21,14 +21,11 @@ class Computer:
         self.output = collections.deque()
 
     def _mode_and_key(self, item: Union[int, Tuple[int, int]]) -> Tuple[int, int]:
-        if type(item) == int:
-            mode = 0
-            key = item
+        if isinstance(item, int):
+            return 0, item
         else:
             mode, key = item
-            key = self.program[self.pointer + key]
-
-        return mode, key
+            return mode, self.program[self.pointer + key]
 
     def __getitem__(self, item: Union[int, Tuple[int, int]]) -> int:
         mode, key = self._mode_and_key(item)
diff --git a/2019/requirements.txt b/2019/requirements.txt
index 5ff3949..3e5cfd1 100644
--- a/2019/requirements.txt
+++ b/2019/requirements.txt
@@ -1,2 +1,3 @@
 pytest
 networkx
+numpy