From 4ed0e540b455273e224661407d9a2eae75574e20 Mon Sep 17 00:00:00 2001
From: Mistivia <i@mistivia.com>
Date: Sun, 22 Dec 2024 20:51:21 +0800
Subject: day 8 part 2

---
 08/2.tcl | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 08/2.tcl

diff --git a/08/2.tcl b/08/2.tcl
new file mode 100644
index 0000000..c52b397
--- /dev/null
+++ b/08/2.tcl
@@ -0,0 +1,73 @@
+set fp [open "input"]
+set lines {}
+while {[gets $fp line] >= 0} {
+    lappend lines $line
+}
+
+close $fp
+
+set height [llength $lines]
+set width [string length [lindex $lines 0]]
+
+proc char_at {x y} {
+    global lines
+    return [string index [lindex $lines $y] $x]
+}
+
+proc in_range {x y} {
+    global height width
+    if {$x < 0 || $x >= $width} {
+        return 0
+    }
+    if {$y < 0 || $y >= $height} {
+        return 0
+    }
+    return 1
+}
+
+proc build_antenna_map {} {
+    global height width
+    set antenna_map {}
+    for {set x 0} {$x < $width} {incr x} {
+        for {set y 0} {$y < $height} {incr y} {
+            set c [char_at $x $y]
+            if {$c == "."} {
+                continue
+            }
+            dict update antenna_map $c site_list {
+                lappend site_list [list $x $y]
+            }
+        }
+    }
+    return $antenna_map
+}
+
+set antenna_map [build_antenna_map]
+set antinodes {}
+
+foreach k [dict keys $antenna_map] {
+    set site_list [dict get $antenna_map $k]
+    set len [llength $site_list]
+    for {set i 0} {$i < $len} {incr i} {
+        for {set j [expr {$i + 1}]} {$j < $len} {incr j} {
+            set x1 [lindex [lindex $site_list $i] 0]
+            set y1 [lindex [lindex $site_list $i] 1]
+            set x2 [lindex [lindex $site_list $j] 0]
+            set y2 [lindex [lindex $site_list $j] 1]
+            set delta_x [expr {$x2 - $x1}]
+            set delta_y [expr {$y2 - $y1}]
+            while {[in_range $x2 $y2]} {
+                dict set antinodes [list $x2 $y2] {}
+                set x2 [expr {$x2 + $delta_x}]
+                set y2 [expr {$y2 + $delta_y}]
+            }
+            while {[in_range $x1 $y1]} {
+                dict set antinodes [list $x1 $y1] {}
+                set x1 [expr {$x1 - $delta_x}]
+                set y1 [expr {$y1 - $delta_y}]
+            }            
+        }
+    }
+}
+
+puts [dict size $antinodes]
-- 
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