16-1

2024/16/16-1.py

@@ -0,0 +1,42 @@
+import networkx as nx
+
+directions = (1, -1, 1j, -1j) # use imaginary numbers for east<->west
+
+with open('2024/16/input.txt') as f:
+    g = nx.DiGraph()
+    for i, line in enumerate(f):
+        line = line.strip()
+        for j, char in enumerate(line):
+            if char == '#':
+                continue
+            node = i + 1j * j
+
+            if char == 'E':
+                e = node
+            if char == 'S':
+                s = (node, 1j) # reindeer starts pointing west
+
+            for nodeDir in directions:
+                g.add_node((node, nodeDir))
+
+    for node, nodeDir in g.nodes:
+        if (node + nodeDir, nodeDir) in g.nodes:
+            # orthogonally connected in the same direction as previous node
+            # eg, connect node A's north direction with node B's north
+            # no need to connect A's north to B's south - it'd be redundant
+            g.add_edge((node, nodeDir), (node + nodeDir, nodeDir), weight=1)
+        for rotation in -1j, 1j:
+            # connect 90 degree corners
+            # using i, since i**2 = 1 so it'll respect a turn
+            g.add_edge((node, nodeDir), (node, nodeDir * rotation), weight=1000)
+
+    # need to make a new endpoint otherwise the exit will not be found
+    for direction in directions:
+        # we appear to have an off-by-one problem, remove the last move to the exit
+        g.add_edge((e, direction), 'end', weight=0)
+
+    shortestPath = nx.shortest_path(g, s, 'end', weight='weight')
+    weight = nx.path_weight(g, shortestPath, weight='weight')
+
+    print(shortestPath)
+    print(weight)

2024/16/testinput.txt

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+###############
+#.......#....E#
+#.#.###.#.###.#
+#.....#.#...#.#
+#.###.#####.#.#
+#.#.#.......#.#
+#.#.#####.###.#
+#...........#.#
+###.#.#####.#.#
+#...#.....#.#.#
+#.#.#.###.#.#.#
+#.....#...#.#.#
+#.###.#.#.#.#.#
+#S..#.....#...#
+###############

2024/16/testinput2.txt

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+#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#.#
+#.#.#.#...#...#.#
+#.#.#.#.###.#.#.#
+#...#.#.#.....#.#
+#.#.#.#.#.#####.#
+#.#...#.#.#.....#
+#.#.#####.#.###.#
+#.#.#.......#...#
+#.#.###.#####.###
+#.#.#...#.....#.#
+#.#.#.#####.###.#
+#.#.#.........#.#
+#.#.#.#########.#
+#S#.............#
+#################