Day 15

Author: r0f1

README.md

@@ -16,6 +16,7 @@
 |[Day 12: Hill Climbing Algorithm](https://adventofcode.com/2022/day/12) |[py](/day12/main.py)|
 |[Day 13: Distress Signal](https://adventofcode.com/2022/day/13)         |[py](/day13/main.py)|
 |[Day 14: Regolith Reservoir](https://adventofcode.com/2022/day/14)      |[py](/day14/main.py)|
+|[Day 15: Beacon Exclusion Zone](https://adventofcode.com/2022/day/15)   |[py](/day15/main.py)|
 
 My solutions from previous years:
 * [r0f1/adventofcode2020](https://github.com/r0f1/adventofcode2020)

day15/main.py

@@ -0,0 +1,48 @@
+import re
+from more_itertools import pairwise
+
+cityblock = lambda x1, y1, x2, y2: abs(x1-x2) + abs(y1-y2)
+
+# file_name = "test.txt"
+# row_part1 = 10
+# xy_bounds = (0, 20)
+
+file_name = "input.txt"
+row_part1 = 2_000_000
+xy_bounds = (0, 4_000_000)
+
+with open(file_name) as f:
+    data = [[int(x) for x in re.findall("-?\d+", l)] for l in f]
+    
+sensors_beacons = set((sx, sy) for sx, sy, _, _ in data) | set((bx, by) for _, _, bx, by in data)
+
+for row in range(*xy_bounds):
+    intervals = []
+    for sx, sy, bx, by in data:
+        d = cityblock(sx, sy, bx, by) - cityblock(sx, sy, sx, row)
+        if d >= 0:
+            intervals.append((sx-d, sx+d))
+
+    res = []
+    s, e = 0, 0
+    for i, ((lb1, ub1), (lb2, ub2)) in enumerate(pairwise(sorted(intervals))):
+        if i == 0:
+            s, e = lb1, ub1
+        if lb2 <= (e+1):
+            e = max(e, ub2)
+        else:
+            res.append((s, e))
+            s, e = lb2, ub2
+    res.append((s, e))
+
+    if row == row_part1:
+        n_beacons_in_row = len(set((bx, by) for _, _, bx, by in data if by == row))
+        print(sum([ub-lb+1 for lb, ub in res]) - n_beacons_in_row)
+
+    reduced = [(lb, ub) for lb, ub in res if ub >= xy_bounds[0] and lb <= xy_bounds[1]]
+    if len(reduced) == 1:
+        continue
+    
+    x, y = reduced[0][1]+1, row
+    if (x, y) not in sensors_beacons:
+        print(4_000_000*x+y)