From 94bf752568cdc9e23c1cdf48f7b984fa2432285e Mon Sep 17 00:00:00 2001
From: Andrew Ekstedt <andrew.ekstedt@gmail.com>
Date: Sat, 16 Dec 2023 06:02:16 +0000
Subject: [PATCH] day 16 part 2

---
 day16/sol.tcl | 55 +++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 45 insertions(+), 10 deletions(-)

diff --git a/day16/sol.tcl b/day16/sol.tcl
index e22babd..5d27703 100755
--- a/day16/sol.tcl
+++ b/day16/sol.tcl
@@ -24,17 +24,19 @@ proc mark-visited {visitp x y d} {
     return $result
 }
 
-proc follow {gridp visitp beams} {
+proc follow {gridp visitp beams {first 0}} {
     upvar $gridp grid
     upvar $visitp visit
     set newbeams {}
     foreach {x y d} $beams {
-        if { [mark-visited visit $x $y $d] } continue
-        switch $d {
-            n { incr y -1 }
-            s { incr y +1 }
-            w { incr x -1 }
-            e { incr x +1 }
+        if {!$first} {
+            if { [mark-visited visit $x $y $d] } continue
+            switch $d {
+                n { incr y -1 }
+                s { incr y +1 }
+                w { incr x -1 }
+                e { incr x +1 }
+            }
         }
         if {![info exists grid($y,$x)]} continue
         switch -exact "$grid($y,$x) $d" {
@@ -60,14 +62,15 @@ proc follow {gridp visitp beams} {
 
 proc solve {} {
     global grid
-    set beams {-1 0 e}
+    set beams [follow grid visit {0 0 e} 1]
     while {[llen $beams] > 0} {
         set beams [follow grid visit $beams]
     }
     set t 0
-    for {set i 0} {$i < 110} {incr i} {
+    set N 10
+    for {set i 0} {$i < $N} {incr i} {
         set row {}
-        for {set j 0} {$j < 110} {incr j} {
+        for {set j 0} {$j < $N} {incr j} {
             if {[info exists visit($i,$j)] && $visit($i,$j)} {
                 lappend row "#"
                 incr t
@@ -80,8 +83,40 @@ proc solve {} {
     puts [array size visit]
 }
 
+proc lmax {list} {
+    set t 0
+    foreach x $list { if {$t < $x} {set t $x} }
+    return $t
+}
+
+proc solve2 {width height} {
+    global grid
+    set edges {}
+    foreach k [array names grid] {
+        lassign [split $k ","] y x
+        if {$x == 0} { lappend edges [list $x $y e] }
+        if {$y == 0} { lappend edges [list $x $y s] }
+        if {$x == $width - 1} { lappend edges [list $x $y n] }
+        if {$y == $height - 1} { lappend edges [list $x $y w] }
+    }
+
+    set l {}
+    foreach beams $edges {
+        array unset visit
+        set beams [follow grid visit $beams 1]
+        while {[llen $beams] > 0} {
+            set beams [follow grid visit $beams]
+        }
+        puts [array size visit]
+        lappend l [array size visit]
+    }
+
+    puts [lmax $l]
+}
+
 read-input grid stdin
 puts [array get grid]
 puts [follow grid visit {0 0 e}]
 
 solve
+solve2 110 110