🪽

VERSION

@@ -1 +1 @@
-🐶
+🪽

y2023/p17.py

@@ -0,0 +1,55 @@
+text = open(0).read()
+graph = {
+    complex(x, y): int({'.': 1, '#': 10000}.get(val, val))
+    for y, row in enumerate(text.splitlines())
+    for x, val in enumerate(row)
+}
+xmax = max(int(p.real) for p in graph)
+ymax = max(int(p.imag) for p in graph)
+end = complex(xmax, ymax)
+mapping = {1: '>', -1: '<', 1j: 'v', -1j: '^'}
+
+# a position mapped to the lowest effort taken to reach it
+edge = {(0, ''): (0, '')}
+exhausted = {}
+while end not in exhausted:
+    pos = min(edge, key=edge.get)
+    parent = edge.pop(pos)
+    if pos[0] == end:
+        break
+    exhausted[pos] = parent
+    for step in [1, -1, 1j, -1j]:
+        # no reverse
+        if pos[1] and pos[1][-1] == mapping[-step]: continue
+
+        # turn condition
+        bop = pos[1] + mapping[step]
+        if len(bop) == 4 and len(set(bop)) == 1: continue
+
+        adj = pos[0] + step, bop[-3:]
+
+        # out of bounds check
+        if adj[0] not in graph: continue
+
+        # some positions are truly dead
+        if adj in exhausted: continue
+
+        score = parent[0] + graph[adj[0]], parent[1] + mapping[step]
+        if adj not in edge:
+            edge[adj] = score
+        else:
+            edge[adj] = min(edge[adj], score)
+
+
+def scorer(seq):
+    pos = 0
+    out = 0
+    for char in seq:
+        pos += {'>': 1, '<': -1, '^': -1j, 'v': 1j}[char]
+        out += graph[pos]
+    return out
+
+
+print(parent[1], scorer(parent[1]))
+test = '>>>v>>>^>>>vv>vv>vvv>vvv<vv>'
+print(test, scorer(test))