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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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