Update day 15.

2022/day15.py

@@ -4,8 +4,72 @@ import sys
 
 import numpy as np
 import parse
+
+
+def part1(sensor_to_beacon: dict[tuple[int, int], tuple[int, int]], row: int) -> int:
+
+    no_beacons_row_l: list[np.ndarray] = []
+
+    for (sx, sy), (bx, by) in sensor_to_beacon.items():
+        d = abs(sx - bx) + abs(sy - by)  # closest
+
+        no_beacons_row_l.append(sx - np.arange(0, d - abs(sy - row) + 1))
+        no_beacons_row_l.append(sx + np.arange(0, d - abs(sy - row) + 1))
+
+    beacons_at_row = set(bx for (bx, by) in sensor_to_beacon.values() if by == row)
+    no_beacons_row = set(np.concatenate(no_beacons_row_l)).difference(beacons_at_row)
+
+    return len(no_beacons_row)
+
+
+def part2_intervals(
+    sensor_to_beacon: dict[tuple[int, int], tuple[int, int]], xy_max: int
+) -> tuple[int, int, int]:
+    from tqdm import trange
+
+    for y in trange(xy_max + 1):
+        its: list[tuple[int, int]] = []
+        for (sx, sy), (bx, by) in sensor_to_beacon.items():
+            d = abs(sx - bx) + abs(sy - by)
+            dx = d - abs(sy - y)
+
+            if dx >= 0:
+                its.append((max(0, sx - dx), min(sx + dx, xy_max)))
+
+        its = sorted(its)
+        s, e = its[0]
+
+        for si, ei in its[1:]:
+            if si > e + 1:
+                return si - 1, y, 4_000_000 * (si - 1) + y
+            if ei > e:
+                e = ei
+
+    return (0, 0, 0)
+
+
+def part2_cplex(
+    sensor_to_beacon: dict[tuple[int, int], tuple[int, int]], xy_max: int
+) -> tuple[int, int, int]:
     from docplex.mp.model import Model
 
+    m = Model()
+
+    x, y = m.continuous_var_list(2, ub=xy_max, name=["x", "y"])
+
+    for (sx, sy), (bx, by) in sensor_to_beacon.items():
+        d = abs(sx - bx) + abs(sy - by)
+        m.add_constraint(m.abs(x - sx) + m.abs(y - sy) >= d + 1, ctname=f"ct_{sx}_{sy}")
+
+    m.set_objective("min", x + y)
+
+    s = m.solve()
+
+    vx = int(s.get_value(x))
+    vy = int(s.get_value(y))
+    return vx, vy, 4_000_000 * vx + vy
+
+
 lines = sys.stdin.read().splitlines()
 
 sensor_to_beacon: dict[tuple[int, int], tuple[int, int]] = {}
@@ -19,33 +83,8 @@ for line in lines:
 xy_max = 4_000_000 if max(sensor_to_beacon) > (1_000, 0) else 20
 row = 2_000_000 if max(sensor_to_beacon) > (1_000, 0) else 10
 
-no_beacons_row_l: list[np.ndarray] = []
+print(f"answer 1 is {part1(sensor_to_beacon, row)}")
 
-for (sx, sy), (bx, by) in sensor_to_beacon.items():
-    d = abs(sx - bx) + abs(sy - by)  # closest
-
-    no_beacons_row_l.append(sx - np.arange(0, d - abs(sy - row) + 1))
-    no_beacons_row_l.append(sx + np.arange(0, d - abs(sy - row) + 1))
-
-beacons_at_row = set(bx for (bx, by) in sensor_to_beacon.values() if by == row)
-no_beacons_row = set(np.concatenate(no_beacons_row_l)).difference(beacons_at_row)
-
-print(f"answer 1 is {len(no_beacons_row)}")
-
-# === part 2 ===
-
-m = Model()
-
-x, y = m.continuous_var_list(2, ub=xy_max, name=["x", "y"])
-
-for (sx, sy), (bx, by) in sensor_to_beacon.items():
-    d = abs(sx - bx) + abs(sy - by)
-    m.add_constraint(m.abs(x - sx) + m.abs(y - sy) >= d + 1, ctname=f"ct_{sx}_{sy}")
-
-m.set_objective("min", x + y)
-
-s = m.solve()
-
-# 10621647166538
-answer_2 = 4_000_000 * int(s.get_value(x)) + int(s.get_value(y))
-print(f"answer 2 is {answer_2}")
+# x, y, a2 = part2_cplex(sensor_to_beacon, xy_max)
+x, y, a2 = part2_intervals(sensor_to_beacon, xy_max)
+print(f"answer 2 is {a2} (x={x}, y={y})")