From 55158903e6d52cda228f1f233c09878a302d9ccc Mon Sep 17 00:00:00 2001
From: Andrew Ekstedt <andrew.ekstedt@gmail.com>
Date: Sun, 10 Dec 2023 07:37:50 +0000
Subject: [PATCH] day 10 much faster fill with numpy

---
 day10/sol.py | 46 +++++++++++++++++++++-------------------------
 1 file changed, 21 insertions(+), 25 deletions(-)

diff --git a/day10/sol.py b/day10/sol.py
index 137f617..9cb6545 100644
--- a/day10/sol.py
+++ b/day10/sol.py
@@ -64,7 +64,9 @@ def find_loop(grid, start):
 
 def enclosedby(grid, points):
     # upsample by 3x3
-    fill = [[0]*(X*3) for _ in range(Y*3)]
+    import numpy
+    fill = numpy.zeros((Y*3,X*3+1), dtype='uint8')
+    #fill = [[0]*(X*3) for _ in range(Y*3)]
     for i,j in points:
         d = grid[i,j]
         if   d == N|S: t=[[0,1,0],[0,1,0],[0,1,0]]
@@ -76,7 +78,7 @@ def enclosedby(grid, points):
         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]
+                fill[i*3+k, j*3+l] = t[k][l]
 
     def draw(fill):
         for row in fill:
@@ -86,39 +88,33 @@ def enclosedby(grid, points):
 
     # 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
+        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
+        if fill[  0  , j] == 0: fill[  0  , j] = 2
+        if fill[Y*3-1, j] == 0: fill[Y*3-1, j] = 2
 
     # flood fill
-    next = {}
-    def set(i,j):
-        if 0 <= i < Y*3 and 0 <= j < X*3:
-            if fill[i][j] == 0:
-                next[i,j] = 2
-    while True:
+    changed = True
+    while changed:
         #draw(fill)
-        next.clear()
+        changed = False
         for i in range(Y*3):
-            for j in range(X*3):
-                if fill[i][j] == 2:
-                    set(i-1,j)
-                    set(i+1,j)
-                    set(i,j-1)
-                    set(i,j+1)
-        if next:
-            for (i,j),c in next.items():
-                fill[i][j] = c
-            continue
-        break
+            f = (fill[i] == 2)
+            f = numpy.roll(f, 1) | numpy.roll(f, -1)
+            if i > 0:     f |= (fill[i-1] == 2)
+            if i < Y*3-1: f |= (fill[i+1] == 2)
+            f[-1] = False
+            f &= (fill[i] == 0)
+            if f.any():
+                fill[i, f] = 2
+                changed = True
     draw(fill)
 
     # 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)]
+        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))