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### Re: Custom Sort An AoA

by davido (Archbishop)
 on Apr 01, 2014 at 18:30 UTC ( #1080621=note: print w/replies, xml ) Need Help??

in reply to Custom Sort An AoA

This solution doesn't optimize for minimizing work inside the sort routine, but I think it does optimize for clarity and generality (it would be easy to substitute <=> for cmp, for example):

```use Test::More tests => 1;

my @unsorted = (
[ 'blah', 'asdf', 'foo', 'bar' ],
['two'], [ 'zzz', 'def', 'ghi' ],
['one'],
[ 'mmm', 'def', 'ghi' ],
[ 'qqq', 'xyz', 'aaa' ]
);

my @wanted = (
['one'], ['two'],
[ 'qqq', 'xyz', 'aaa' ],
[ 'mmm', 'def', 'ghi' ],
[ 'zzz', 'def', 'ghi' ],
[ 'blah', 'asdf', 'foo', 'bar' ]
);

my @sorted = sort {
@\$a <=> @\$b
|| do {
my ( \$left, \$right ) = ( [@\$a], [@\$b] );
my \$res = 0;
\$res = pop(@\$left) cmp pop(@\$right) while @\$left && !\$res;
\$res;
};
} @unsorted;

diag "@{\$_}\n" for @sorted;

is_deeply( \@sorted, \@wanted, 'Sorted array matches expectation.' );

Output.........

```1..1
# one
# two
# qqq xyz aaa
# mmm def ghi
# zzz def ghi
# blah asdf foo bar
ok 1 - Sorted array matches expectation.

Update: Here's a version that doesn't waste time making copies of the elements for the purpose of pop:

```use Test::More tests => 1;

my @unsorted = (
[ 'blah', 'asdf', 'foo', 'bar' ],
['two'], [ 'zzz', 'def', 'ghi' ],
['one'],
[ 'mmm', 'def', 'ghi' ],
[ 'qqq', 'xyz', 'aaa' ]
);

my @wanted = (
['one'], ['two'],
[ 'qqq', 'xyz', 'aaa' ],
[ 'mmm', 'def', 'ghi' ],
[ 'zzz', 'def', 'ghi' ],
[ 'blah', 'asdf', 'foo', 'bar' ]
);

my @sorted = sort {
my \$res;
@\$a <=> @\$b ||
do { \$res = \$a->[\$_] cmp \$b->[\$_] and return \$res for reverse 0 .. \$
+#{\$a} };
} @unsorted;

diag "@{\$_}\n" for @sorted;

is_deeply( \@sorted, \@wanted, 'Sorted array matches expectation.' );

Same output as above.

Dave

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