day 17 part 1 (hellishly slow)

17/pseudo

@@ -0,0 +1,56 @@
+Graph.Edges(u@dir, v@dir) {
+    ; if cost(v) = 0xff, we're off graph,
+    ; in the padded area
+    Graph.Edges := cost(v)
+}
+
+v@dir(u, dir) {
+    v.dir := dir
+    tmp := 1
+    bt dir, 3
+    if CF
+        tmp := LINE_LEN
+    bt dir, 2
+    if CF
+        tmp := -tmp
+    v := u + tmp
+}
+
+neighbors(u@dir) {
+    ; can always turn
+    neighbors += v@dir(u, ~u.dir & 0b1000)
+    neighbors += v@dir(u, (~u.dir & 0b1000) | 0b0100)
+    ; can go forward if consec < 3
+    if u.dir & 0b0011 < 3
+        neighbors += v@dir(u, u.dir + 1)
+}
+
+; 12 possibilities, use 16 so we can do bit hacks
+;      0000  0001  0010  0011  0100  0101  0110  0111   
+;         0     1     2     3     4     5     6     7    
+dir = {  R1,   R2,   R3,   XX,   L1,   L2,   L3,   XX,   
+;      1000  1001  1010  1011  1100  1101  1110  1111
+;         8     9    10    11    12    13    14    15  
+         D1,   D2,   D3,   XX,   U1,   U2,   U3,   XX} 
+
+dist[(x,y),dir]
+prev[(x,y),dir]
+   q[(x,y),dir]
+
+for each vertex v in Graph.Vertices:
+  dist[v] ← INFINITY
+  prev[v] ← UNDEFINED
+  add v to Q
+
+for all real dir:
+    dist[source@dir] ← 0
+
+while Q is not empty and any dist[u] in Q < inf:
+  u ← vertex in Q with min dist[u]
+  remove u from Q
+  for each neighbor v of u still in Q:
+    alt ← dist[u] + Graph.Edges(u, v)
+    if alt < dist[v]:
+        dist[v] ← alt
+        prev[v] ← u
+done