Day 15

Author: Iain530

2022/15/beacon_exclusion_zone.py

@@ -0,0 +1,78 @@
+from utils import read_input, run
+from collections import Counter
+
+
+FNAME = "15/input.txt"
+
+
+def parse_line(line):
+    return [tuple(int(coord.rstrip(',')[2:]) for coord in item.split(' ')[-2:]) for item in line.split(':')]
+
+
+##########
+# PART 1 #
+##########
+
+def distance(c1, c2):
+    x1, y1 = c1
+    x2, y2 = c2
+    return abs(x2 - x1) + abs(y2 - y1)
+
+
+def find_not_possible(data, target_y):
+    not_possible = set()
+
+    for sensor, beacon in data:
+        x, y = sensor
+        dist = distance(sensor, beacon)
+        remaining_dist = dist - abs(target_y - y)
+        if remaining_dist >= 0:
+            not_possible |= {x + i for i in range(-remaining_dist, remaining_dist)}
+    
+    return not_possible
+
+
+def part_one(input_file):
+    data = read_input(input_file, parse_chunk=parse_line)
+    return len(find_not_possible(data, 2_000_000))
+
+##########
+# PART 2 #
+##########
+
+
+def is_correct(data, coord):
+    return all(distance(sensor, coord) > distance(sensor, beacon) for sensor, beacon in data)
+
+
+def find_outer_coords(counter: Counter, sensor, beacon):
+    dist = distance(sensor, beacon) + 1
+    x, y = sensor
+
+    # Possible optimisation: just store the lines for each square
+    # only consider points that intersect
+    for i in range(dist):
+        for edge_x in (x + dist - i, x - dist + i):
+            for edge_y in (y-i, y+i):
+                if 0 <= edge_x <= 4_000_000 and 0 <= edge_y <= 4_000_000:
+                    counter[(edge_x, edge_y)] += 1
+
+    return counter
+
+
+def part_two(input_file):
+    data = read_input(input_file, parse_chunk=parse_line)
+    counts = Counter()
+
+    for sensor, beacon in data:
+        find_outer_coords(counts, sensor, beacon)
+
+    if answer := next((p for p in counts if counts[p] >= 4 and is_correct(data, p)), None):
+        x, y = answer
+        return x * 4_000_000 + y
+    
+    return None
+
+
+if __name__ == '__main__':
+    run(part_one, part_two, FNAME)

2022/15/input.txt

@@ -0,0 +1,29 @@
+Sensor at x=2389280, y=2368338: closest beacon is at x=2127703, y=2732666
+Sensor at x=1882900, y=3151610: closest beacon is at x=2127703, y=2732666
+Sensor at x=2480353, y=3555879: closest beacon is at x=2092670, y=3609041
+Sensor at x=93539, y=965767: closest beacon is at x=501559, y=361502
+Sensor at x=357769, y=2291291: closest beacon is at x=262473, y=2000000
+Sensor at x=2237908, y=1893142: closest beacon is at x=2127703, y=2732666
+Sensor at x=2331355, y=3906306: closest beacon is at x=2092670, y=3609041
+Sensor at x=3919787, y=2021847: closest beacon is at x=2795763, y=2589706
+Sensor at x=3501238, y=3327244: closest beacon is at x=3562181, y=3408594
+Sensor at x=1695968, y=2581703: closest beacon is at x=2127703, y=2732666
+Sensor at x=3545913, y=3356504: closest beacon is at x=3562181, y=3408594
+Sensor at x=1182450, y=1405295: closest beacon is at x=262473, y=2000000
+Sensor at x=3067566, y=3753120: closest beacon is at x=3562181, y=3408594
+Sensor at x=1835569, y=3983183: closest beacon is at x=2092670, y=3609041
+Sensor at x=127716, y=2464105: closest beacon is at x=262473, y=2000000
+Sensor at x=3065608, y=3010074: closest beacon is at x=2795763, y=2589706
+Sensor at x=2690430, y=2693094: closest beacon is at x=2795763, y=2589706
+Sensor at x=2051508, y=3785175: closest beacon is at x=2092670, y=3609041
+Sensor at x=2377394, y=3043562: closest beacon is at x=2127703, y=2732666
+Sensor at x=1377653, y=37024: closest beacon is at x=501559, y=361502
+Sensor at x=2758174, y=2627042: closest beacon is at x=2795763, y=2589706
+Sensor at x=1968468, y=2665146: closest beacon is at x=2127703, y=2732666
+Sensor at x=3993311, y=3779031: closest beacon is at x=3562181, y=3408594
+Sensor at x=159792, y=1923149: closest beacon is at x=262473, y=2000000
+Sensor at x=724679, y=3489022: closest beacon is at x=2092670, y=3609041
+Sensor at x=720259, y=121267: closest beacon is at x=501559, y=361502
+Sensor at x=6, y=46894: closest beacon is at x=501559, y=361502
+Sensor at x=21501, y=2098549: closest beacon is at x=262473, y=2000000
+Sensor at x=2974083, y=551886: closest beacon is at x=4271266, y=-98555

2022/README.md

@@ -13,6 +13,8 @@
 - [Day 11 - Monkey in the Middle](./11/monkey_in_the_middle.py)
 - [Day 12 - Hill Climbing Algorithm](./12/hill_climbing_algorithm.py)
 - [Day 13 - Distress Signal](./13/distress_signal.py)
+- [Day 14 - Regolith Reservoir](./14/regolith_reservoir.py)
+- [Day 15 - Beacon Exclusion Zone](./15/beacon_exclusion_zone.py)
 
 ```bash
 # Run solutions as a module from this directory