day 10 part 2

day10/sample10.in

@@ -0,0 +1,9 @@
+...........
+.S-------7.
+.|F-----7|.
+.||.....||.
+.||.....||.
+.|L-7.F-J|.
+.|..|.|..|.
+.L--J.L--J.
+...........

day10/sample15.in

@@ -0,0 +1,10 @@
+FF7FSF7F7F7F7F7F---7
+L|LJ||||||||||||F--J
+FL-7LJLJ||||||LJL-77
+F--JF--7||LJLJ7F7FJ-
+L---JF-JLJ.||-FJLJJ7
+|F|F-JF---7F7-L7L|7|
+|FFJF7L7F-JF7|JL---7
+7-L-JL7||F7|L7F-7F7|
+L.L7LFJ|||||FJL7||LJ
+L7JLJL-JLJLJL--JLJ.L

day10/sol.py

@@ -63,10 +63,72 @@ def find_loop(grid, start):
 
     return dist
 
+def enclosedby(grid, points):
+    # upsample by 3x3
+    fill = {}
+    for i,j in grid:
+        for k in range(3):
+            for l in range(3):
+                fill[i*3+k,j*3+l] = 0
+    print(*sorted(fill.keys()), sep="\n")
+    for i,j in points:
+        d = grid[i,j]
+        if   d == N|S: t=[[0,1,0],[0,1,0],[0,1,0]]
+        elif d == N|W: t=[[0,1,0],[1,1,0],[0,0,0]]
+        elif d == N|E: t=[[0,1,0],[0,1,1],[0,0,0]]
+        elif d == S|W: t=[[0,0,0],[1,1,0],[0,1,0]]
+        elif d == S|E:t=[[0,0,0],[0,1,1],[0,1,0]]
+        elif d == E|W:t=[[0,0,0],[1,1,1],[0,0,0]]
+        else: raise Exception("invalid d=%d at (%s,%s)" % (d, i, j))
+        for k in range(3):
+            for l in range(3):
+                fill[i*3+k,j*3+l] = t[k][l]
+    print(fill)
+
+    # fill edges
+    for i in range(Y*3):
+        if fill[i,0] == 0: fill[i,0] = 2
+        if fill[i,X*3-1] == 0: fill[i,X*3-1] = 2
+    for j in range(X*3):
+        if fill[0,j] == 0: fill[0,j] = 2
+        if fill[Y*3-1,j] == 0: fill[Y*3-1,j] = 2
+
+    # flood fill
+    while True:
+        #for i in range(Y*3):
+            #print("".join(".+O"[fill[i,j]] for j in range(X*3)))
+        next = fill.copy()
+        def set(i,j):
+            if (i,j) in fill:
+                if fill[i,j] == 0:
+                    next[i,j] = 2
+        for i,j in fill:
+            if fill[i,j] == 2:
+                set(i-1,j)
+                set(i+1,j)
+                set(i,j-1)
+                set(i,j+1)
+        if next == fill:
+            break
+        fill = next
+    for i in range(Y*3):
+        print("".join(".+O"[fill[i,j]] for j in range(X*3)))
+
+    # downsample
+    inside = []
+    for i,j in grid:
+        f = [fill[i*3+k,j*3+l]==0 for k in range(3) for l in range(3)]
+        if all(f):
+            inside.append((i,j))
+
+
+    print(inside)
+    return len(inside)
+
 for D in [W|S, N|W, N|E, S|E, N|S, W|E]:
     grid[start] = D
     loop = find_loop(grid, start)
     if loop:
         print(D, loop)
         print(max(loop.values()))
-    
+        print(enclosedby(grid, loop))