Solutions days 23, 25 from 2023 (#20)

* Solution day 23

* Solve day 25

Author: mkopec87

src/2023/23/2023_23.py

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+import itertools
+from typing import Tuple
+
+import networkx as nx
+import numpy as np
+from tqdm import tqdm
+
+from src.utils.data import load_data
+from src.utils.submission import submit_or_print
+
+ROCK = "#"
+
+N = (-1, 0)
+S = (1, 0)
+W = (0, -1)
+E = (0, 1)
+
+
+def main(debug: bool) -> None:
+    input_data = load_data(debug)
+
+    grid, start, end = parse_grid(input_data)
+
+    result_part1 = solve_part1(grid, start, end)
+    result_part2 = solve_part2(grid, start, end)
+
+    submit_or_print(result_part1, result_part2, debug)
+
+
+def parse_grid(input_data: str) -> Tuple[np.array, Tuple[int, int], Tuple[int, int]]:
+    rows = []
+    for line in input_data.strip().splitlines():
+        rows.append(list(line))
+
+    # borders
+    rows.append(["#" for _ in rows[0]])
+    rows.insert(0, ["#" for _ in rows[0]])
+
+    grid = np.array(rows)
+
+    # search for start and end positions
+    start = 1, [y for y in range(grid.shape[1]) if grid[1, y] == "."][0]
+    end = (
+        grid.shape[0] - 2,
+        [y for y in range(grid.shape[1]) if grid[grid.shape[0] - 2, y] == "."][0],
+    )
+
+    return grid, start, end
+
+
+def solve_part1(grid: np.array, start: Tuple[int, int], end: Tuple[int, int]) -> int:
+    graph = create_graph(grid)
+    return max(map(len, nx.all_simple_paths(graph, start, end))) - 1
+
+
+def solve_part2(grid: np.array, start: Tuple[int, int], end: Tuple[int, int]) -> int:
+    graph = create_graph(grid, part2=True)
+
+    print("Compressing graph...")
+    compressed_graph = compress(graph)
+    print("Initial graph:   ", graph)
+    print("Compressed graph:", compressed_graph)
+
+    viz_path = "graph.png"
+    pos = nx.planar_layout(compressed_graph)
+    nx.draw(compressed_graph, pos, with_labels=True)
+    import matplotlib.pyplot as plt
+
+    plt.savefig(viz_path)
+    print(f"Saved compressed graph visualization to: {viz_path}")
+
+    print("Searching for longest path in compressed graph...")
+    return max(
+        map(
+            lambda path: nx.path_weight(compressed_graph, path, "weight"),
+            nx.all_simple_paths(compressed_graph, start, end),
+        )
+    )
+
+
+def create_graph(grid: np.array, part2: bool = False) -> nx.Graph:
+    graph = nx.Graph() if part2 else nx.DiGraph()
+    for x, y in np.ndindex(grid.shape):
+        if grid[x, y] != ROCK:
+            graph.add_node((x, y))
+    for x, y in np.ndindex(grid.shape):
+        p = grid[x, y]
+        if p != ROCK:
+            if part2:
+                p = "."
+
+            match p:
+                case ">":
+                    dirs = [E]
+                case "<":
+                    dirs = [W]
+                case "^":
+                    dirs = [N]
+                case "v":
+                    dirs = [S]
+                case _:
+                    dirs = [N, S, W, E]
+
+            for d in dirs:
+                n_pos = d[0] + x, d[1] + y
+                n = grid[n_pos]
+                if n != ROCK:
+                    graph.add_edge((x, y), n_pos, weight=1)
+    return graph
+
+
+def compress(graph: nx.Graph) -> nx.Graph:
+    crossroads = {node for node in graph.nodes if len(graph.edges(node)) != 2}
+
+    compressed_graph = nx.Graph(graph)
+    for p1, p2 in tqdm(list(itertools.combinations(crossroads, 2))):
+        # simplified graph without crossroads
+        graph_copy = nx.Graph(graph)
+        for c in crossroads:
+            if c not in {p1, p2}:
+                graph_copy.remove_node(c)
+
+        # find all paths
+        for path in nx.all_simple_paths(graph_copy, p1, p2):
+            if len(path) < 3:
+                continue
+            weight = len(path) - 1
+            compressed_graph.add_edge(p1, p2, weight=weight)
+            for n in path[1:-1]:
+                compressed_graph.remove_node(n)
+    return compressed_graph
+
+
+if __name__ == "__main__":
+    debug_mode = True
+    # debug_mode = False
+    main(debug_mode)

src/2023/23/sample_input.txt

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+#.#######
+#>......#
+#.###.#.#
+#....>..#
+#######.#

src/2023/25/2023_25.py

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+import math
+import re
+
+import matplotlib.pyplot as plt
+import networkx as nx
+
+from src.utils.data import load_data
+from src.utils.submission import submit_or_print
+
+
+def main(debug: bool) -> None:
+    input_data = load_data(debug)
+
+    graph = parse_graph(input_data)
+    print(graph)
+
+    viz_path = "graph.png"
+    pos = nx.spring_layout(graph)
+    nx.draw(graph, pos, with_labels=True)
+    plt.savefig(viz_path)
+    print(f"Saved graph visualization to: {viz_path}")
+
+    edges = nx.edge_betweenness_centrality(graph)
+    top3 = sorted(edges.items(), key=lambda k: k[1], reverse=True)[:3]
+    for e, _ in top3:
+        graph.remove_edge(*e)
+    print(f"Removed 3 key edges: {[t[0] for t in top3]}")
+
+    result_part1 = math.prod([len(c) for c in nx.connected_components(graph)])
+    result_part2 = None
+
+    submit_or_print(result_part1, result_part2, debug)
+
+
+def parse_graph(input_data: str) -> nx.Graph:
+    graph = nx.Graph()
+    for line in input_data.strip().splitlines():
+        nodes = re.findall(r"[a-z]+", line)
+        for node in nodes[1:]:
+            graph.add_edge(nodes[0], node)
+    return graph
+
+
+if __name__ == "__main__":
+    debug_mode = True
+    # debug_mode = False
+    main(debug_mode)

src/2023/25/graph.png

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+a: b c d e
+e: f g h a
+f: b g h
+h: d g f
+b: f c d
+d: h b c