Add day20, 2024

Author: snhansen

2024/day20/solution.py

@@ -0,0 +1,36 @@
+from itertools import combinations
+
+with open("input") as f:
+    inp = f.read().strip().split("\n")
+
+
+track = set()
+for i, l in enumerate(inp):
+    for j, x in enumerate(l):
+        if x != "#":
+            track.add(j + i*1j)
+        if x == "S":
+            start = j + i*1j
+        if x == "E":
+            end = j + i*1j
+
+dirs = [1, -1, 1j, -1j]
+times = {start: 0}
+q = [start]
+while q:
+    p = q.pop()
+    for dp in dirs:
+        if p + dp not in track or p + dp in times.keys():
+            continue
+        times[p + dp] = times[p] + 1
+        q.append(p + dp)
+
+pt1, pt2 = 0, 0
+for p1, p2 in combinations(times.keys(), 2):
+    dist = abs(p1.real - p2.real) + abs(p1.imag - p2.imag)
+    if dist <= 2:
+        pt1 += (times[end] - (times[p1] + times[end] - times[p2] + dist) >= 100)
+    if dist <= 20:
+        pt2 += (times[end] - (times[p1] + times[end] - times[p2] + dist) >= 100)
+
+print(pt1, pt2)