diff options
| -rw-r--r-- | 06/1.tcl | 1 | ||||
| -rw-r--r-- | 06/2.tcl | 125 |
2 files changed, 126 insertions, 0 deletions
@@ -12,6 +12,7 @@ while {1} { } lappend map $line } +close $fp proc char_at {x y} { set line [lindex $::map $y] diff --git a/06/2.tcl b/06/2.tcl new file mode 100644 index 0000000..0efa76f --- /dev/null +++ b/06/2.tcl @@ -0,0 +1,125 @@ +#!/usr/bin/env tclsh + +set fp [open input r] +set map "" +while {1} { + set ret [gets $fp line] + if {$ret == -1} { + break + } + if {[string length $line] == 0} { + break + } + lappend map $line +} +close $fp + +proc char_at {x y} { + set line [lindex $::map $y] + return [string index $line $x] +} + +set height [llength $map] +set width [string length [lindex $map 0]] + +proc find_start {} { + for {set i 0} {$i < $::width} {incr i} { + for {set j 0} {$j < $::height} {incr j} { + if {[char_at $i $j] == "^"} { + return "$i $j" + } + } + } +} + +set start_point [find_start] + +proc front_point {x y direction} { + if {$direction == "up"} { + return [list $x [expr {$y - 1}]] + } elseif {$direction == "down"} { + return [list $x [expr {$y + 1}]] + } elseif {$direction == "left"} { + return [list [expr {$x - 1}] $y] + } elseif {$direction == "right"} { + return [list [expr {$x + 1}] $y] + } +} + +proc out_of_range {x y} { + return [expr { + ($x < 0) || ($x >= $::width) || ($y < 0) || ($y >= $::height) + }] +} + +proc turn_right {direction} { + if {$direction == {up}} { + return right + } elseif {$direction == {down}} { + return left + } elseif {$direction == {right}} { + return down + } else { + return up + } +} + + +proc next_state {x y direction} { + set forward [front_point $x $y $direction] + if {[out_of_range {*}$forward]} { + return [list {*}$forward $direction] + } + while {[char_at {*}$forward] == {#}} { + set forward [front_point $x $y [turn_right $direction]] + set direction [turn_right $direction] + } + return [list {*}$forward $direction] +} + + +proc will_loop {} { + global start_point + set state [list {*}$start_point up] + set past_states {} + while {1} { + if {[out_of_range {*}[lrange $state 0 1]]} { + return 0 + } + if {[dict exists $past_states $state]} { + return 1 + } + dict set past_states $state { } + set state [next_state {*}$state] + } +} + +proc set_obstruction {x y} { + global map + set orig_line [lindex $map $y] + lset map $y [string replace $orig_line $x $x "#"] +} + +proc clear_obstruction {x y} { + global map + set orig_line [lindex $map $y] + lset map $y [string replace $orig_line $x $x "."] +} + +set count 0 +for {set i 0} {$i < $width} {incr i} { + for {set j 0} {$j < $height} {incr j} { + if {[char_at $i $j] == "^"} { + continue + } + if {[char_at $i $j] == "#"} { + continue + } + set_obstruction $i $j + if {[will_loop]} { + set count [expr {$count + 1}] + } + clear_obstruction $i $j + } +} +puts $count |