Day 15

day15/part1.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+import re
+
+lines = (x.strip() for x in open("input.txt"))
+target = 2000000
+intervals = []
+known_targets = set()
+
+for line in lines:
+    x, y, a, b = map(int, re.search(r"(-?\d+).+?(-?\d+).+?(-?\d+).+?(-?\d+)", line).groups())
+    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)
+
+print(sum(b-a+1 for a, b in merged)-len(known_targets))