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#!/usr/bin/perl -w |
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|
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# symmetry.pl |
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# |
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# 08/26/07 02:40:37 CEST Dobrica Pavlinusic <dpavlin@rot13.org> |
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use strict; |
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|
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my $board = << '_BOARD_'; |
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+-+-+-+-+-+-+-+-+ |
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| | |o| | | |
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+ + +-+ +-+ | |
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|o| | o | o | |
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+ + +-+ +-+ | |
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| | o | | | |
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+-+-+ +-+-+-+-+ |
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| | |o| | |
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+-+ + +-+-+ +-+ |
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| |o| |o|o|o|o| |
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+ + +-+-+-+-+ +-+ |
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|o| | | | |
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+ +-+-+-+-+-+-+-+ |
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| | o | |
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+-+-+-+-+-+-+-+-+ |
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| o | o | |
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+-+-+-+-+-+-+-+-+ |
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_BOARD_ |
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|
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my @board = map { split(//) } split(/\n/, $board); |
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|
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# line length |
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my $ll = 8 * 2 + 1; |
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|
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sub draw { |
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my @board = @_; |
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my $o = 0; |
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my $out; |
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while ( $o < $#board ) { |
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$out .= join('', @board[ $o .. $o + $ll - 1 ]) . "\n"; |
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$o += $ll; |
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} |
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return $out; |
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} |
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|
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print $board, draw( @board ); |
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|
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my @step_name = ( qw/right down left up/ ); |
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my @move_by = ( 1, $ll, -1, -$ll ); |
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my $step = 0; # right |
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|
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# offset 0, top-left corner |
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my $pos = shift @ARGV || 0; |
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|
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my @trace = ('x') x ( $#board + 1 ); |
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sub trace { |
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warn "trace $pos\n"; |
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$trace[ $pos ] = $board[ $pos ]; |
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} |
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|
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warn draw( @trace ); |
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trace; |
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|
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sub move { |
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warn "move $step $step_name[$step]\n"; |
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$pos += $move_by[ $step ]; |
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trace; |
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$pos += $move_by[ $step ]; |
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trace; |
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warn draw( @trace ); |
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} |
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|
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sub follow { |
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$step = shift; |
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$step %= 4; |
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warn "follow $step $step_name[$step]\n"; |
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} |
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|
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my $ok_path = qr/[\|\-]/; |
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|
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sub can_turn { |
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my $try_step = shift; |
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die "no step?" unless defined $try_step; |
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|
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$try_step %= 4; |
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|
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my $turn_pos = $pos + $move_by[$try_step]; |
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|
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my $old = $trace[ $turn_pos ]; |
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$trace[ $turn_pos ] = '?'; |
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warn "TEST\n",draw( @trace ); |
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$trace[ $turn_pos ] = $old; |
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|
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if ( $board[ $turn_pos ] =~ $ok_path ) { |
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warn "OK can_turn $try_step $step_name[$try_step] turn_pos = $turn_pos b($board[$turn_pos]) t($trace[$turn_pos])"; |
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$step = $try_step; |
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return 1; |
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} else { |
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warn "NOPE can_turn $try_step $step_name[$try_step] turn_pos = $turn_pos b($board[$turn_pos]) t($trace[$turn_pos])"; |
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return 0; |
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} |
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} |
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|
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while( 1 ) { |
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|
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my $next_pos = $pos + $move_by[ $step ]; |
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warn "in loop - pos = $pos next_pos = $next_pos step = $step $step_name[$step]\n"; |
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|
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if ( $trace[ $next_pos ] ne 'x' ) { |
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warn "position $next_pos re-visited, exiting\n"; |
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last; |
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} elsif ( $board[ $next_pos ] =~ $ok_path ) { |
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warn "OK next_pos = $next_pos b($board[$next_pos]) t($trace[$next_pos])\n"; |
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move; |
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can_turn( $step + 1 ); |
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} else { |
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warn "find line continuation from $step $step_name[$step]...\n"; |
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can_turn( $step - 1 ) || can_turn( $step + 1 ) || die "can't find new direction"; |
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} |
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warn draw( @trace ); |
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|
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} |
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|
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warn "ended at $pos\n"; |
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