adding day 20 2024

2024/day20/code.py

@@ -1,8 +1,11 @@
 # pylint: disable=C0114,C0116,C0301,C0209,W1514,C0414,E0001
 
+
+from itertools import product
 from typing import Any
 import os
 from time import perf_counter_ns
+import heapq
 
 input_file = os.path.join(os.path.dirname(__file__), "input.txt")
 # input_file = os.path.join(os.path.dirname(__file__), "test.txt")
@@ -24,16 +27,78 @@ def wrapper_method(*args: Any, **kwargs: Any) -> Any:
     return wrapper_method
 
 
+def dijkstra(start, free_spaces):
+    to_visit = []
+    visited = {
+        (start): 0,
+    }
+
+    heapq.heappush(to_visit, (0, start))
+
+    while to_visit:
+        score, (cx, cy) = heapq.heappop(to_visit)
+
+        if (cx, cy) in visited and visited[(cx, cy)] < score:
+            continue
+
+        for dx, dy in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
+            if (cx+dx, cy+dy) in free_spaces:
+                np = (cx+dx, cy+dy)
+                if np not in visited or visited[np] > score + 1:
+                    visited[np] = score + 1
+                    heapq.heappush(to_visit, (score+1, np))
+
+    return visited
+
+
+def get_savings(distances, jump_size, free_space):
+    ret = 0
+    for p in free_space:
+        for dx, dy in product(range(-jump_size, jump_size+1), repeat=2):
+            if dx == dy == 0 or abs(dx) + abs(dy) > jump_size:
+                continue
+            np = (p[0]+dx, p[1]+dy)
+            if np in free_space:
+                no_walls_cost = abs(p[0]-np[0]) + abs(p[1]-np[1])
+                all_walls_cost = distances[np] - distances[p]
+
+                if (all_walls_cost - no_walls_cost) >= 100:
+                    ret += 1
+    return ret
+
+
 @profiler
 def part_1():
-    with open(input_file) as _f:
-        pass
+    free_space = set()
+    end = None
+    with open(input_file) as f:
+        for y, line in enumerate(f):
+            for x, c in enumerate(line):
+                if c in ".SE":
+                    free_space.add((x, y))
+                if c == "E":
+                    end = (x, y)
+
+    from_end = dijkstra(end, free_space)
+
+    print(get_savings(from_end, 2, free_space))
 
 
 @profiler
 def part_2():
-    with open(input_file) as _f:
-        pass
+    free_space = set()
+    end = None
+    with open(input_file) as f:
+        for y, line in enumerate(f):
+            for x, c in enumerate(line):
+                if c in ".SE":
+                    free_space.add((x, y))
+                if c == "E":
+                    end = (x, y)
+
+    from_end = dijkstra(end, free_space)
+
+    print(get_savings(from_end, 20, free_space))
 
 
 if __name__ == "__main__":

2024/day20/test.txt

@@ -0,0 +1,15 @@
+###############
+#...#...#.....#
+#.#.#.#.#.###.#
+#S#...#.#.#...#
+#######.#.#.###
+#######.#.#...#
+#######.#.###.#
+###..E#...#...#
+###.#######.###
+#...###...#...#
+#.#####.#.###.#
+#.#...#.#.#...#
+#.#.#.#.#.#.###
+#...#...#...###
+###############