From b0d458b72e1e214bc89c6e3aaa012e95b1a91b9d Mon Sep 17 00:00:00 2001
From: Jake Pullen <jake_pullen@live.co.uk>
Date: Sat, 23 Dec 2023 09:14:01 +0000
Subject: [PATCH] day 23 Done

---
 2023/23/part 1 solution.py | 107 ++++++++++++++++++++++++++++++++++
 2023/23/part 2 solution.py | 115 +++++++++++++++++++++++++++++++++++++
 2 files changed, 222 insertions(+)
 create mode 100644 2023/23/part 1 solution.py
 create mode 100644 2023/23/part 2 solution.py

diff --git a/2023/23/part 1 solution.py b/2023/23/part 1 solution.py
new file mode 100644
index 0000000..7edd4d9
--- /dev/null
+++ b/2023/23/part 1 solution.py	
@@ -0,0 +1,107 @@
+import sys
+from collections import deque
+
+with open(r'advent_of_code\2023\23\input.txt', 'r') as file:
+    input = file.read()
+
+test_input = '''#.#####################
+#.......#########...###
+#######.#########.#.###
+###.....#.>.>.###.#.###
+###v#####.#v#.###.#.###
+###.>...#.#.#.....#...#
+###v###.#.#.#########.#
+###...#.#.#.......#...#
+#####.#.#.#######.#.###
+#.....#.#.#.......#...#
+#.#####.#.#.#########v#
+#.#...#...#...###...>.#
+#.#.#v#######v###.###v#
+#...#.>.#...>.>.#.###.#
+#####v#.#.###v#.#.###.#
+#.....#...#...#.#.#...#
+#.#########.###.#.#.###
+#...###...#...#...#.###
+###.###.#.###v#####v###
+#...#...#.#.>.>.#.>.###
+#.###.###.#.###.#.#v###
+#.....###...###...#...#
+#####################.#'''
+
+# Set recursion limit
+sys.setrecursionlimit(10**6)
+
+# Read input
+input_data = input
+lines = input_data.split('\n')
+
+# Create grid from input
+grid = [[char for char in row] for row in lines]
+num_rows = len(grid)
+num_cols = len(grid[0])
+
+# Directions for navigation
+directions = [['^',-1,0],['v', 1,0],['<', 0,-1],['>',0,1]]
+
+def solve():
+    # Set of vertices
+    vertices = set()
+
+    # Identify vertices
+    for row in range(num_rows):
+        for col in range(num_cols):
+            num_neighbors = sum(1 for char,dr,dc in directions if 0<=row+dr<num_rows and 0<=col+dc<num_cols and grid[row+dr][col+dc]!='#')
+            if num_neighbors>2 and grid[row][col]!='#':
+                vertices.add((row,col))
+
+    # Identify start and end points
+    start, end = None, None
+    for col in range(num_cols):
+        if grid[0][col]=='.':
+            vertices.add((0,col))
+            start = (0,col)
+        if grid[num_rows-1][col]=='.':
+            vertices.add((num_rows-1,col))
+            end = (num_rows-1,col)
+
+    # Create edges
+    edges = {vertex: [] for vertex in vertices}
+    for vertex in vertices:
+        queue = deque([(vertex[0],vertex[1],0)])
+        seen = set()
+        while queue:
+            r,c,d = queue.popleft()
+            if (r,c) in seen:
+                continue
+            seen.add((r,c))
+            if (r,c) in vertices and (r,c) != vertex:
+                edges[vertex].append(((r,c),d))
+                continue
+            for char,dr,dc in directions:
+                if (0<=r+dr<num_rows and 0<=c+dc<num_cols and grid[r+dr][c+dc]!='#'):
+                    if grid[r][c] in ['<', '>', '^', 'v'] and grid[r][c]!=char:
+                        continue
+                    queue.append((r+dr,c+dc,d+1))
+
+    # Depth-first search
+    max_distance = 0
+    seen_grid = [[False for _ in range(num_cols)] for _ in range(num_rows)]
+    def dfs(v,d):
+        nonlocal max_distance
+        r,c = v
+        if seen_grid[r][c]:
+            return
+        seen_grid[r][c] = True
+        if r==num_rows-1:
+            max_distance = max(max_distance, d)
+        for (next_vertex,next_distance) in edges[v]:
+            dfs(next_vertex,d+next_distance)
+        seen_grid[r][c] = False
+
+    # Start DFS from start point
+    dfs(start,0)
+
+    return max_distance
+
+# Print results
+print(solve())
\ No newline at end of file
diff --git a/2023/23/part 2 solution.py b/2023/23/part 2 solution.py
new file mode 100644
index 0000000..daa066d
--- /dev/null
+++ b/2023/23/part 2 solution.py	
@@ -0,0 +1,115 @@
+import sys
+from collections import deque
+
+with open(r'advent_of_code\2023\23\input.txt', 'r') as file:
+    input = file.read()
+
+test_input = '''#.#####################
+#.......#########...###
+#######.#########.#.###
+###.....#.>.>.###.#.###
+###v#####.#v#.###.#.###
+###.>...#.#.#.....#...#
+###v###.#.#.#########.#
+###...#.#.#.......#...#
+#####.#.#.#######.#.###
+#.....#.#.#.......#...#
+#.#####.#.#.#########v#
+#.#...#...#...###...>.#
+#.#.#v#######v###.###v#
+#...#.>.#...>.>.#.###.#
+#####v#.#.###v#.#.###.#
+#.....#...#...#.#.#...#
+#.#########.###.#.#.###
+#...###...#...#...#.###
+###.###.#.###v#####v###
+#...#...#.#.>.>.#.>.###
+#.###.###.#.###.#.#v###
+#.....###...###...#...#
+#####################.#'''
+
+# Set recursion limit
+sys.setrecursionlimit(10**6)
+
+# Read input
+input_data = input
+lines = input_data.split('\n')
+
+# Create grid from input
+grid = [[char for char in row] for row in lines]
+num_rows = len(grid)
+num_cols = len(grid[0])
+
+# Directions for navigation
+directions = [['^',-1,0],['v', 1,0],['<', 0,-1],['>',0,1]]
+
+def solve(is_part1):
+    # Set of vertices
+    vertices = set()
+
+    # Identify vertices
+    for row in range(num_rows):
+        for col in range(num_cols):
+            num_neighbors = 0
+            for char,dr,dc in directions:
+                if (0<=row+dr<num_rows and 0<=col+dc<num_cols and grid[row+dr][col+dc]!='#'):
+                    num_neighbors += 1
+            if num_neighbors>2 and grid[row][col]!='#':
+                vertices.add((row,col))
+
+    # Identify start and end points
+    start, end = None, None
+    for col in range(num_cols):
+        if grid[0][col]=='.':
+            vertices.add((0,col))
+            start = (0,col)
+        if grid[num_rows-1][col]=='.':
+            vertices.add((num_rows-1,col))
+            end = (num_rows-1,col)
+
+    # Create edges
+    edges = {}
+    for vertex in vertices:
+        edges[vertex] = []
+        queue = deque([(vertex[0],vertex[1],0)])
+        seen = set()
+        while queue:
+            r,c,d = queue.popleft()
+            if (r,c) in seen:
+                continue
+            seen.add((r,c))
+            if (r,c) in vertices and (r,c) != vertex:
+                edges[vertex].append(((r,c),d))
+                continue
+            for char,dr,dc in directions:
+                if (0<=r+dr<num_rows and 0<=c+dc<num_cols and grid[r+dr][c+dc]!='#'):
+                    if is_part1 and grid[r][c] in ['<', '>', '^', 'v'] and grid[r][c]!=char:
+                        continue
+                    queue.append((r+dr,c+dc,d+1))
+
+    # Depth-first search
+    count = 0
+    max_distance = 0
+    seen_grid = [[False for _ in range(num_cols)] for _ in range(num_rows)]
+    def dfs(v,d):
+        nonlocal count
+        nonlocal max_distance
+        count += 1
+        r,c = v
+        if seen_grid[r][c]:
+            return
+        seen_grid[r][c] = True
+        if r==num_rows-1:
+            max_distance = max(max_distance, d)
+        for (next_vertex,next_distance) in edges[v]:
+            dfs(next_vertex,d+next_distance)
+        seen_grid[r][c] = False
+
+    # Start DFS from start point
+    dfs(start,0)
+
+    return max_distance
+
+# Print results
+print(solve(True))
+print(solve(False))
\ No newline at end of file