1 files changed, 90 insertions, 0 deletions
diff --git a/2024/tcl/06.tcl b/2024/tcl/06.tcl
new file mode 100755
index 0000000..fa48061
--- /dev/null
+++ b/2024/tcl/06.tcl
@@ -0,0 +1,90 @@
+#!/bin/env tclsh
+
+source lib.tcl
+setup 6
+
+puts {Part 1: Count unique guard coords}
+
+set map(grid) {}
+foreach line $input {
+  lappend map(grid) [split $line ""]
+}
+set map(h) [llength $map(grid)]
+set map(w) [llength [lindex $map(grid) 0]]
+set map(visits) {}
+set map(debug) $map(grid)
+set guard(y) [lsearch $map(grid) *^*]
+set guard(x) [lsearch [lindex $map(grid) $guard(y)] ^]
+set guard(dir) 0
+set placed_obstructions {}
+
+set rot_map {{-1 0} {0 1} {1 0} {0 -1}}
+
+proc step_guard {} {
+  global guard rot_map map
+  dict set map(visits) [list $guard(y) $guard(x)] $guard(dir) 1
+  lset map(debug) $guard(y) $guard(x) [lindex {^ > v <} $guard(dir)]
+
+  lassign [lindex $rot_map $guard(dir)] ydir xdir
+  set ynew [expr {$guard(y) + $ydir}]
+  set xnew [expr {$guard(x) + $xdir}]
+
+  if {$ynew < 0 || $ynew >= $map(h) || $xnew < 0 || $xnew >= $map(w)} { return 0 }
+
+  if {[lindex $map(grid) $ynew $xnew] == "#"} {
+    set guard(dir) [expr {($guard(dir) + 1) % 4}]
+    return 1
+  }
+
+  set guard(y) $ynew
+  set guard(x) $xnew
+  return 1
+}
+
+# sigh
+set potential_loops 0
+while {[step_guard]} {
+  puts -nonewline "Unique coords: [llength [dict keys $map(visits)]]\r"
+  flush stdout
+
+  lassign [lindex $rot_map $guard(dir)] ydir xdir
+  set ynew [expr {$guard(y) + $ydir}]
+  set xnew [expr {$guard(x) + $xdir}]
+  if {$ynew < 0 || $ynew >= $map(h) || $xnew < 0 || $xnew >= $map(w)} continue
+
+  # it took me. 2 hours. to realize i needed the clause after the ||. god dammit.
+  if {[dict exists $placed_obstructions [list $ynew $xnew]] || [dict exists $map(visits) [list $ynew $xnew]]} {
+    continue
+  }
+  if {[dict exists $map(visits) [list $guard(y) $guard(x)] [expr {($guard(dir) + 1) % 4}]]} {
+#    foreach line $map(debug) {
+#      puts [join $line ""]
+#    }
+    dict incr placed_obstructions [list $ynew $xnew] 1
+    incr potential_loops
+  } elseif {[lindex $map(grid) $ynew $xnew] != "#"} {
+    set map_backup [array get map]
+    set guard_backup [array get guard]
+
+    lset map(grid) $ynew $xnew "#"
+    lset map(debug) $ynew $xnew "#"
+
+    while {[step_guard]} {
+      if {[dict exists $map(visits) [list $guard(y) $guard(x)] $guard(dir)]} {
+        dict incr placed_obstructions [list $ynew $xnew] 2
+        incr potential_loops
+        break
+      }
+    }
+
+    array set map $map_backup
+    array set guard $guard_backup
+  }
+}
+
+puts "Unique coords: [llength [dict keys $map(visits)]]"
+
+puts ""
+puts {Part 2: Number of potential looping obstructions}
+
+puts "Potential count: [llength [dict keys $placed_obstructions]]"