From 21f5c917429d9ff9507761ad43200a38d8a7e501 Mon Sep 17 00:00:00 2001
From: FrederikBaerentsen <frederik+gitea@baerentsen.net>
Date: Fri, 6 Dec 2024 22:56:55 +0100
Subject: [PATCH] Optimized 2024/06 P2

---
 2024/06/solution.py | 46 +++++++++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/2024/06/solution.py b/2024/06/solution.py
index c49ef8d..2351a11 100644
--- a/2024/06/solution.py
+++ b/2024/06/solution.py
@@ -77,20 +77,32 @@ if part == 2:
 
     def isLoop(grid,pos,direction):
         positions = []
-        
-        while grid_valid(pos[0],pos[1],grid):
-            #nprint(grid,pos,'X')
-            if get_value_in_direction(grid,pos,direction) != '#':
-                cur = (pos[0],pos[1],direction)
+        count = 0
+        l = len(grid)
 
-                if cur not in positions:
-                    positions.append(cur)
-                else:
-                    return 1
-                pos = (pos[0]+offsets[direction][0],pos[1]+offsets[direction][1])
-            elif get_value_in_direction(grid,pos,direction) == '#':
+        while grid_valid(pos[0],pos[1],grid):
+            next = get_value_in_direction(grid,pos,direction)
+            if next == '#':
                 direction = next_direction[direction]
-            #input()
+            else:
+                cur = (pos[0],pos[1],direction)
+                count += 1
+                
+                # Instead of loging all visited positions and their direction, 
+                # we can break out if we have visited more places than 4x the
+                # grid size (4 being once for each direction).
+                # This actually gives us the right result
+
+                #if cur not in positions:
+                #    positions.append(cur)
+                #elif cur in positions:
+                #    return 1
+
+                if count > 4*l*l:
+                    return 1
+
+                pos = (pos[0]+offsets[direction][0],pos[1]+offsets[direction][1])
+                
         return 0
     
     grid = toGrid(input_f)
@@ -105,7 +117,6 @@ if part == 2:
 
     pos = start
     while grid_valid(pos[0],pos[1],grid):
-
         dir = get_value_in_direction(grid, pos)
         if get_value_in_direction(grid,pos,direction) != '#':
             if pos not in steps:
@@ -115,11 +126,10 @@ if part == 2:
             direction = next_direction[direction]
     steps.remove(start)
     print(len(steps))
+
     result = 0
     for idx,i in enumerate(steps):
-        print(idx)
-        new_grid = grid[:]
-        new_grid[i[0]][i[1]] = '#'
-        result += isLoop(new_grid,start,'up')
-        new_grid[i[0]][i[1]] = '.'
+        grid[i[0]][i[1]] = '#'
+        result += isLoop(grid,start,'up')
+        grid[i[0]][i[1]] = '.'
     print(result)
\ No newline at end of file