Day 15

day15/part2.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+import re
+
+lines = (x.strip() for x in open("input.txt"))
+lines = [tuple(map(int, re.search(r"(-?\d+).+?(-?\d+).+?(-?\d+).+?(-?\d+)", line).groups())) for line in lines]
+
+for target in range(0, 4000000): #3186981
+    if target % 40000 == 0:
+        print(target/4000000)
+    intervals = []
+    known_targets = set()
+
+    for line in lines:
+        x, y, a, b = line
+        dist = abs(x-a) + abs(y-b)
+        width = dist-abs(y-target)
+        if width >= 0:
+            intervals.append((x-width, x+width))
+        if b == target:
+            known_targets.add(a)
+        if y == target:
+            known_targets.add(x)
+
+
+    intervals.sort(key=lambda x: x[0])
+    merged = [intervals[0]]
+    for i in intervals[1:]:
+        if merged[-1][1] >= i[0]:
+            merged[-1] = (merged[-1][0], max(merged[-1][1], i[1]))
+        else:
+            merged.append(i)
+
+    if len(merged) > 1:
+        print(target, merged, (merged[0][1]+1)*4000000+target)
+        break