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use Test;
# Solution algoritm.
# We peel layers (like a cake) from the top, then right, then bottom and left until nothing is left.
# String them together for solution.
# Solution walk through
# Input:
# 1 2 3
# 4 5 6
# 7 8 9
#
# After taking the top layer, it becomes
# 4 5 6
# 7 8 9
#
# Take the right layer off.
# 4 5
# 7 8
#
# Take the bootom layer off
#
# 4 5
#
# Take left layer off.
# 5
#
# Finally tope layer again
#
# []
#
# Collect the removed items in a result list
sub solve(@M) {
my @directions = |<top right bottom left> xx *;
my $num-rows = @M.elems;
my $num-cols = @M[0].elems;
my @result = reduce sub (@acc, $direction){
given $direction {
when 'top' {
@acc.append(@(@M.shift));
}
when 'right' {
my @right-col = do for @M -> $r {
$r.pop;
}
@acc.append(@right-col);
}
when 'bottom' {
@acc.append(@M.pop.reverse);
}
when 'left' {
my @left-col = do for @M -> $c {
$c.shift;
}
@acc.append(@left-col.reverse);
}
}
@acc;
}, [], |@directions[0..^($num-rows + $num-cols -1)];
}
sub MAIN(){
my @M = [[ 1, 2, 3, 4 ],
[ 5, 6, 7, 8 ],
[ 9, 10, 11, 12 ],
[ 13, 14, 15, 16 ]];
say "Problem: ", @M;
say "Solution: ", solve (@M);
say "";
my @M1 = [[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]];
say "Problem: ", @M1;
say "Solution: ", solve (@M1);
}
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