From 7c399251d6650b94d02da5b9956d5fc4b55e62b6 Mon Sep 17 00:00:00 2001
From: Niccolo Borgioli <niccolo.borgioli@lovoo.com>
Date: Thu, 9 Dec 2021 15:35:29 +0100
Subject: [PATCH] 09

---
 2021/09/README.md      |  11 +++
 2021/09/python/main.py | 153 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 164 insertions(+)
 create mode 100644 2021/09/README.md
 create mode 100644 2021/09/python/main.py

diff --git a/2021/09/README.md b/2021/09/README.md
new file mode 100644
index 0000000..64e1bed
--- /dev/null
+++ b/2021/09/README.md
@@ -0,0 +1,11 @@
+# 09
+
+The first was really straight forward. The second was cool as we could do a breadth first search, taking account the edges of our growing basins.
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>439</li>
+    <li>900900</li>
+  </ol>
+</details>
diff --git a/2021/09/python/main.py b/2021/09/python/main.py
new file mode 100644
index 0000000..00b4893
--- /dev/null
+++ b/2021/09/python/main.py
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+#!/usr/bin/env python
+
+from os.path import join, dirname
+from typing import List
+
+# Day 09
+
+# Common
+
+
+def read_input(filename):
+    data = join(dirname(__file__), '..', filename)
+    with open(data) as f:
+        return f.read().strip()
+
+
+test = read_input('test.txt')
+data = read_input('input.txt')
+
+
+def make_string_blue(string):
+    return f'\033[94m{string}\033[0m'
+
+
+def make_string_red(string):
+    return f'\033[91m{string}\033[0m'
+
+
+class Point:
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    def __repr__(self):
+        return f'({self.x}, {self.y})'
+
+    def __hash__(self) -> int:
+        return hash((self.x, self.y))
+
+    def __eq__(self, o: object) -> bool:
+        if not isinstance(o, Point):
+            return False
+        return self.x == o.x and self.y == o.y
+
+    def value(self, data: List[List[int]]):
+        return data[self.y][self.x]
+
+
+class Floor:
+    def __init__(self, data: List[List[int]]):
+        self.data = data
+        self.max_x = len(data[0])
+        self.max_y = len(data)
+
+    def paint(self, blue: List[Point] = [], red: List[Point] = []) -> str:
+        out = ''
+        for y in range(self.max_y):
+            for x in range(self.max_x):
+                v = str(self.data[y][x])
+                if Point(x, y) in red:
+                    v = f'\033[31m{v}\033[0m'
+                elif Point(x, y) in blue:
+                    v = f'\033[34m{v}\033[0m'
+                out += v
+            out += '\n'
+        return out
+
+    def get_neighbors(self, point: Point) -> List[Point]:
+        neighbors = []
+        if point.x - 1 >= 0:
+            neighbors.append(Point(point.x - 1, point.y))
+        if point.x + 1 < self.max_x:
+            neighbors.append(Point(point.x + 1, point.y))
+        if point.y - 1 >= 0:
+            neighbors.append(Point(point.x, point.y - 1))
+        if point.y + 1 < self.max_y:
+            neighbors.append(Point(point.x, point.y + 1))
+        return neighbors
+
+    def find_lowest_points(self) -> List[Point]:
+        lowest_points = []
+        for y in range(self.max_y):
+            for x in range(self.max_x):
+                p = Point(x, y)
+                neighbors = self.get_neighbors(p)
+                values = [p.value(self.data) for p in neighbors]
+                if p.value(self.data) < min(values):
+                    lowest_points.append(p)
+        return lowest_points
+
+    def find_basins(self):
+        lowest = self.find_lowest_points()
+        basins = []
+        for point in lowest:
+            basin = set([point])
+            edges = set([point])
+            while len(edges) > 0:
+                new_edges = set()
+                for edge in edges:
+                    neighbors = self.get_neighbors(edge)
+                    for neighbor in neighbors:
+                        if neighbor not in basin and neighbor.value(self.data) < 9:
+                            basin.add(neighbor)
+                            new_edges.add(neighbor)
+                edges = new_edges
+            basins.append(basin)
+        print(self.paint(
+            [point for basin in basins for point in basin], lowest))
+        return basins
+
+    def flag2(self) -> int:
+        basins = self.find_basins()
+        sizes = [len(b) for b in basins]
+        sizes = sorted(sizes, reverse=True)
+        total = 1
+        for size in sizes[0:3]:
+            total *= size
+        return total
+
+    def flag(self) -> int:
+        points = self.find_lowest_points()
+        return sum([
+            p.value(self.data) + 1
+            for p in points
+        ])
+
+    @staticmethod
+    def parse(data: str):
+        return Floor([
+            list(map(int, list(row)))
+            for row in data.split('\n')
+        ])
+
+
+# 1
+print('1.')
+
+floor = Floor.parse(test)
+print(floor.paint(floor.find_lowest_points()))
+print(f'Test: {floor.flag()}')
+
+floor = Floor.parse(data)
+print(floor.paint(floor.find_lowest_points()))
+print(f'Real: {floor.flag()}')
+
+# 2
+print('\n2.')
+
+floor = Floor.parse(test)
+print(f'Test: {floor.flag2()}')
+
+floor = Floor.parse(data)
+print(f'Real: {floor.flag2()}')