From 65ef6c9debe652e87dce6f1906cfd020577de61e Mon Sep 17 00:00:00 2001
From: Pavel Karateev <lancelote.du.lac@gmail.com>
Date: Sat, 16 Dec 2023 13:51:32 +0100
Subject: [PATCH] 2023 day 10 part 1

---
 README.md                         |  2 +-
 src/year2023/day10a.py            | 87 +++++++++++++++++++++++++++++++
 tests/src/year2023/test_day10a.py | 30 +++++++++++
 3 files changed, 118 insertions(+), 1 deletion(-)
 create mode 100644 src/year2023/day10a.py
 create mode 100644 tests/src/year2023/test_day10a.py

diff --git a/README.md b/README.md
index 437d8aa..ae164f0 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@
 - 2020 - ★★★★★ ★★★★★ ★★★★★ ☆
 - 2021 - ★★★★★ ★★★★★ ★★★★★ ★★★
 - 2022 - ★★★★★ ★★★★★ ★★★★★ ★☆
-- 2023 - ★★★★☆ ★☆★★
+- 2023 - ★★★★☆ ★☆★★☆
 
 ## How to use
 
diff --git a/src/year2023/day10a.py b/src/year2023/day10a.py
new file mode 100644
index 0000000..40c073c
--- /dev/null
+++ b/src/year2023/day10a.py
@@ -0,0 +1,87 @@
+"""2023 - Day 10 Part 1: Pipe Maze"""
+from collections import defaultdict
+from typing import TypeAlias
+
+C: TypeAlias = tuple[int, int]
+Map: TypeAlias = dict[C, set[C]]
+Land: TypeAlias = list[list[str]]
+
+# | - L J 7 F . S
+N_CONN = {"S", "|", "L", "J"}
+E_CONN = {"S", "-", "L", "F"}
+S_CONN = {"S", "|", "7", "F"}
+W_CONN = {"S", "-", "7", "J"}
+
+
+def construct_map(land: Land) -> Map:
+    rows = len(land)
+    cols = len(land[0])
+
+    m: dict[C, set[C]] = defaultdict(set)
+
+    for r in range(rows):
+        for c in range(cols):
+            # N
+            if r > 0 and land[r][c] in N_CONN and land[r - 1][c] in S_CONN:
+                m[(r, c)].add((r - 1, c))
+
+            # E
+            if (
+                c < cols - 1
+                and land[r][c] in E_CONN
+                and land[r][c + 1] in W_CONN
+            ):
+                m[(r, c)].add((r, c + 1))
+
+            # S
+            if (
+                r < rows - 1
+                and land[r][c] in S_CONN
+                and land[r + 1][c] in N_CONN
+            ):
+                m[(r, c)].add((r + 1, c))
+
+            # W
+            if c > 0 and land[r][c] in W_CONN and land[r][c - 1] in E_CONN:
+                m[(r, c)].add((r, c - 1))
+
+    return m
+
+
+def process_data(data: str) -> Land:
+    return [list(x) for x in data.splitlines()]
+
+
+def get_path(prev: C, curr: C, m: Map, land: Land) -> int:
+    path = 0
+
+    while land[curr[0]][curr[1]] != "S":
+        nxt_set = m[curr] - {prev}
+
+        if len(nxt_set) == 0:
+            return -1  # dead end
+
+        prev = curr
+        (curr,) = nxt_set
+        path += 1
+
+    return path
+
+
+def find_start(land: Land) -> C:
+    rows = len(land)
+    cols = len(land[0])
+
+    for r in range(rows):
+        for c in range(cols):
+            if land[r][c] == "S":
+                return r, c
+
+    raise ValueError("start position wasn't found")
+
+
+def solve(task: str) -> int:
+    land = process_data(task)
+    m = construct_map(land)
+    start = find_start(land)
+    return max(get_path(start, x, m, land) for x in m[start]) // 2 + 1
diff --git a/tests/src/year2023/test_day10a.py b/tests/src/year2023/test_day10a.py
new file mode 100644
index 0000000..b226945
--- /dev/null
+++ b/tests/src/year2023/test_day10a.py
@@ -0,0 +1,30 @@
+"""2023 - Day 10 Part 1: Pipe Maze"""
+from textwrap import dedent
+
+from src.year2023.day10a import solve
+
+
+def test_solve_0():
+    task = dedent(
+        """
+        .....
+        .S-7.
+        .|.|.
+        .L-J.
+        .....
+        """
+    ).strip()
+    assert solve(task) == 4
+
+
+def test_solve_1():
+    task = dedent(
+        """
+        ..F7.
+        .FJ|.
+        SJ.L7
+        |F--J
+        LJ...
+        """
+    ).strip()
+    assert solve(task) == 8