Added solution for 2023/Day 23

.github/website/2023/index.html

@@ -150,8 +150,8 @@ <h1>Advent of Code 2023</h1>
 				</tr>
 				<tr>
 					<td><a href="https://github.com/npanuhin/Advent-of-Code/tree/master/2023/Day%2023">Day 23</a></td>
-					<td></td>
-					<td></td>
+					<td><a href="https://github.com/npanuhin/Advent-of-Code/tree/master/2023/Day%2023/part1.py">⭐</a></td>
+					<td><a href="https://github.com/npanuhin/Advent-of-Code/tree/master/2023/Day%2023/part2.py">⭐</a></td>
 				</tr>
 				<tr>
 					<td><a href="https://github.com/npanuhin/Advent-of-Code/tree/master/2023/Day%2024">Day 24</a></td>

2023/Day 23/part1.py

@@ -0,0 +1,44 @@
+from sys import setrecursionlimit
+
+
+setrecursionlimit(10 ** 6)
+
+DIRECTIONS = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+
+
+with open('input.txt') as file:
+    terrain = list(filter(None, map(str.strip, file)))
+
+width, height = len(terrain[0]), len(terrain)
+
+start_y, start_x = 0, terrain[0].index('.')
+
+
+def find_logest_path(x: int, y: int, visited: list[list[bool]]) -> int:
+    if y == height - 1:
+        return 0
+
+    length = float('-inf')
+
+    visited[y][x] = True
+
+    for dy, dx in DIRECTIONS:
+        if not (0 <= x + dx < width and 0 <= y + dy < height) or visited[y + dy][x + dx]:
+            continue
+
+        if any((
+            terrain[y + dy][x + dx] == '.',
+            terrain[y + dy][x + dx] == '>' and dx == 1,
+            terrain[y + dy][x + dx] == '<' and dx == -1,
+            terrain[y + dy][x + dx] == '^' and dy == -1,
+            terrain[y + dy][x + dx] == 'v' and dy == 1
+        )):
+            length = max(length, find_logest_path(x + dx, y + dy, visited))
+
+    visited[y][x] = False
+
+    return length + 1
+
+
+visited = [[False] * width for _ in range(height)]
+print(find_logest_path(start_x, start_y, visited))

2023/Day 23/part2.py

@@ -0,0 +1,68 @@
+from collections import defaultdict
+
+
+DIRECTIONS = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+
+
+with open('input.txt') as file:
+    terrain = list(filter(None, map(str.strip, file)))
+
+width, height = len(terrain[0]), len(terrain)
+
+start_y, start_x = 0, terrain[0].index('.')
+end_y, end_x = height - 1, terrain[height - 1].index('.')
+
+
+def get_neighbours(x: int, y: int) -> list[tuple[int, int]]:
+    yield from (
+        (x + dx, y + dy)
+        for dy, dx in DIRECTIONS
+        if 0 <= x + dx < width and 0 <= y + dy < height
+    )
+
+
+def find_intersections(x, y, prev=None, distance=0):
+    if prev and sum(terrain[test_y][test_x] != '#' for test_x, test_y in get_neighbours(x, y)) > 2:
+        yield ((x, y), distance)
+        return
+
+    for new_x, new_y in get_neighbours(x, y):
+        if (new_x, new_y) == prev:
+            continue
+
+        if terrain[new_y][new_x] != '#':
+            yield from find_intersections(new_x, new_y, (x, y), distance + 1)
+
+
+first_intersection, before_first_distance = next(find_intersections(start_x, start_y))
+last_intersection, after_last_distance = next(find_intersections(end_x, end_y))
+
+intesections_graph = defaultdict(dict)
+todo = [first_intersection]
+while todo:
+    x, y = todo.pop()
+    intesections_graph[y][x] = list(find_intersections(x, y))
+    todo.extend(
+        (x, y)
+        for (x, y), _ in intesections_graph[y][x]
+        if x not in intesections_graph.get(y, [])
+    )
+
+
+def find_logest_path(x: int, y: int, visited: list[list[bool]]) -> int:
+    if (x, y) == last_intersection:
+        return 0
+
+    length = float('-inf')
+    visited[y][x] = True
+
+    for (new_x, new_y), distance in intesections_graph[y][x]:
+        if not visited[new_y][new_x]:
+            length = max(length, find_logest_path(new_x, new_y, visited) + distance)
+
+    visited[y][x] = False
+    return length
+
+
+visited = [[False] * width for _ in range(height)]
+print(before_first_distance + find_logest_path(*first_intersection, visited) + after_last_distance)

2023/Day 23/solution.py

@@ -0,0 +1,102 @@
+from collections import defaultdict
+from sys import setrecursionlimit
+
+
+setrecursionlimit(10 ** 6)
+
+DIRECTIONS = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+
+
+def get_neighbours(x: int, y: int) -> list[tuple[int, int]]:
+    yield from (
+        (x + dx, y + dy)
+        for dy, dx in DIRECTIONS
+        if 0 <= x + dx < width and 0 <= y + dy < height
+    )
+
+
+def part1(terrain):
+    def find_logest_path(x: int, y: int, visited: list[list[bool]]) -> int:
+        if y == height - 1:
+            return 0
+
+        length = float('-inf')
+
+        visited[y][x] = True
+
+        for dy, dx in DIRECTIONS:
+            if not (0 <= x + dx < width and 0 <= y + dy < height) or visited[y + dy][x + dx]:
+                continue
+
+            if any((
+                terrain[y + dy][x + dx] == '.',
+                terrain[y + dy][x + dx] == '>' and dx == 1,
+                terrain[y + dy][x + dx] == '<' and dx == -1,
+                terrain[y + dy][x + dx] == '^' and dy == -1,
+                terrain[y + dy][x + dx] == 'v' and dy == 1
+            )):
+                length = max(length, find_logest_path(x + dx, y + dy, visited))
+
+        visited[y][x] = False
+
+        return length + 1
+
+    visited = [[False] * width for _ in range(height)]
+    return find_logest_path(start_x, start_y, visited)
+
+
+def part2(terrain):
+    def find_intersections(x, y, prev=None, distance=0):
+        if prev and sum(terrain[test_y][test_x] != '#' for test_x, test_y in get_neighbours(x, y)) > 2:
+            yield ((x, y), distance)
+            return
+
+        for new_x, new_y in get_neighbours(x, y):
+            if (new_x, new_y) == prev:
+                continue
+
+            if terrain[new_y][new_x] != '#':
+                yield from find_intersections(new_x, new_y, (x, y), distance + 1)
+
+    first_intersection, before_first_distance = next(find_intersections(start_x, start_y))
+    last_intersection, after_last_distance = next(find_intersections(end_x, end_y))
+
+    intesections_graph = defaultdict(dict)
+    todo = [first_intersection]
+    while todo:
+        x, y = todo.pop()
+        intesections_graph[y][x] = list(find_intersections(x, y))
+        todo.extend(
+            (x, y)
+            for (x, y), _ in intesections_graph[y][x]
+            if x not in intesections_graph.get(y, [])
+        )
+
+    def find_logest_path(x: int, y: int, visited: list[list[bool]]) -> int:
+        if (x, y) == last_intersection:
+            return 0
+
+        length = float('-inf')
+        visited[y][x] = True
+
+        for (new_x, new_y), distance in intesections_graph[y][x]:
+            if not visited[new_y][new_x]:
+                length = max(length, find_logest_path(new_x, new_y, visited) + distance)
+
+        visited[y][x] = False
+        return length
+
+    visited = [[False] * width for _ in range(height)]
+    return before_first_distance + find_logest_path(*first_intersection, visited) + after_last_distance
+
+
+with open('input.txt') as file:
+    terrain = list(filter(None, map(str.strip, file)))
+
+width, height = len(terrain[0]), len(terrain)
+
+start_y, start_x = 0, terrain[0].index('.')
+end_y, end_x = height - 1, terrain[height - 1].index('.')
+
+print(part1(terrain))
+print(part2(terrain))

2023/README.md

@@ -126,16 +126,16 @@
 	</tr>
 	<tr>
 		<td>Day 23: A Long Walk</td>
-		<td align="center"></td>
-		<td align="center"></td>
+		<td align="center"><a href="Day%2023/part1.py">⭐</a></td>
+		<td align="center"><a href="Day%2023/part2.py">⭐</a></td>
 	</tr>
 	<tr>
 		<td>Day 24: Never Tell Me The Odds</td>
 		<td align="center"></td>
 		<td align="center"></td>
 	</tr>
 	<tr>
-		<td>Day 25</td>
+		<td>Day 25: Snowverload</td>
 		<td align="center" colspan="2"></td>
 	</tr>
 </table>

README.md

@@ -158,7 +158,7 @@ I try to optimize each solution as much as possible, so although they are writte
 		<td>Day 23</td>
 		<td align="center"><a href="2020/Day%2023/part1.py">⭐</a><a href="2020/Day%2023/part2.py">⭐</a></td>
 		<td align="center"><a href="2021/Day%2023/part1.py">⭐</a><a href="2021/Day%2023/part2.py">⭐</a></td>
-		<td align="center"></td>
+		<td align="center"><a href="2023/Day%2023/part1.py">⭐</a><a href="2023/Day%2023/part2.py">⭐</a></td>
 	</tr>
 	<tr>
 		<td>Day 24</td>