Solve day 12

2022/12_climb.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+import sys
+from heapq import heappop, heappush
+
+def parse(content):
+    grid = [ord(x) - ord('a') for x in content if x != '\n']
+    w = content.find('\n')
+    src = grid.index(ord('S') - ord('a'))
+    dst = grid.index(ord('E') - ord('a'))
+    grid[src] = 0
+    grid[dst] = 25
+    return grid, w, src, dst
+
+def closest_starts(grid, w, dst):
+    h = len(grid) // w
+    def neighbors(i):
+        y, x = divmod(i, w)
+        if x > 0: yield i - 1
+        if x < w - 1: yield i + 1
+        if y > 0: yield i - w
+        if y < h - 1: yield i + w
+
+    dist = [1 << 31] * len(grid)
+    dist[dst] = 0
+    worklist = [(0, dst)]
+
+    while worklist:
+        udist, u = heappop(worklist)
+        if udist == dist[u]:
+            for v in neighbors(u):
+                if grid[u] <= grid[v] + 1:
+                    alt = dist[u] + 1
+                    if alt < dist[v]:
+                        dist[v] = alt
+                        heappush(worklist, (alt, v))
+    return dist
+
+grid, w, src, dst = parse(sys.stdin.read())
+dist = closest_starts(grid, w, dst)
+print(dist[src])
+print(min(d for elev, d in zip(grid, dist) if not elev))

2022/input/12

@@ -0,0 +1,41 @@
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