Solve 2024:18 p1-2 "RAM Run"

BFS baby.

FIRST_BLOCKED was found manually using code from pt 1
to perform a binary search.

2024-python/output/day_18.py

@@ -0,0 +1,90 @@
+from collections import deque
+
+from output import ints, D
+
+
+def solve(data):
+    grid = [tuple(ints(line)[::-1]) for line in data.splitlines()]
+    sample_size = 1024
+    H = 71
+    W = 71
+    E = H - 1, W - 1
+    p1 = None
+    p2 = None
+    FIRST_BLOCKED = 2974
+    for sample_size in [1024, FIRST_BLOCKED]:
+        answer = None
+        Q = deque([(0, 0, 0)])
+        seen = set()
+        while Q:
+            y, x, w = Q.popleft()
+            if (y, x) in seen:
+                continue
+            seen.add((y, x))
+            if (y, x) == E:
+                answer = w
+            for dy, dx in D:
+                if not (0 <= y + dy < H and 0 <= x + dx < W):
+                    continue
+                if (y + dy, x + dx) in grid[:sample_size]:
+                    continue
+                Q.append((y + dy, x + dx, w + 1))
+        if not answer:
+            r, c = grid[sample_size - 1]
+            p2 = f"{c},{r}"
+        else:
+            p1 = answer
+    return p1, p2
+
+
+if __name__ == "__main__":
+    import os
+
+    # use dummy data
+    inp = """
+    5,4
+    4,2
+    4,5
+    3,0
+    2,1
+    6,3
+    2,4
+    1,5
+    0,6
+    3,3
+    2,6
+    5,1
+    1,2
+    5,5
+    2,5
+    6,5
+    1,4
+    0,4
+    6,4
+    1,1
+    6,1
+    1,0
+    0,5
+    1,6
+    2,0
+    """.strip()
+
+    # uncomment to instead use stdin
+    # import sys; inp = sys.stdin.read().strip()
+
+    # uncomment to use AoC provided puzzle input
+    with open("./input/18.txt", "r") as f:
+        inp = f.read().strip()
+
+    # uncomment to do initial data processing shared by part 1-2
+    p1, p2 = solve(inp)
+
+    print(p1)
+    os.system(f"echo {p1} | wl-copy")
+    print(p2)
+    os.system(f"echo {p2} | wl-copy")
+
+    # uncomment and replace 0 with actual output to refactor code
+    # and ensure nonbreaking changes
+    # assert p1 == 0
+    # assert p2 == 0