| Algorithm-MinMax documentation | Contained in the Algorithm-MinMax distribution. |
Algorithm::MinMax - Finding the minimum and maximum of an array with at most 3n/2 - 2 comparisons.
use Algorithm::MinMax; @a = ( 3, 2, 5, 4, 8, 9 ); @r = Algorithm::MinMax->minmax( \@a ); # $r[0] = minimum = 2 # $r[1] = maximum = 9
The implementation finds the minimum and maximum of a given array with at most 3n/2 - 2 comparisons, where n is the number of elements of the array.
Returns an array where the first entry is the minimum and the second entry the maximum of the given array.
If minmax is called with an empty array, minmax will also return an empty array.
Daniel Etzold, detzold@gmx.de
| Algorithm-MinMax documentation | Contained in the Algorithm-MinMax distribution. |
package Algorithm::MinMax; use 5.6.1; use strict; use warnings; require Exporter; our @ISA = qw(Exporter); # Items to export into callers namespace by default. Note: do not export # names by default without a very good reason. Use EXPORT_OK instead. # Do not simply export all your public functions/methods/constants. # This allows declaration use Algorithm::MinMax ':all'; # If you do not need this, moving things directly into @EXPORT or @EXPORT_OK # will save memory. our %EXPORT_TAGS = ( 'all' => [ qw( ) ] ); our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } ); our @EXPORT = qw( ); our $VERSION = '0.01'; # Preloaded methods go here. sub minmax { my @array = @{ $_[ 1 ] }; my @result; if( scalar( @array ) == 0 ) { return @result; } if( scalar( @array ) == 1 ) { $result[ 0 ] = $array[ 0 ]; $result[ 1 ] = $array[ 0 ]; return @result; } my @min_cand; my @max_cand; my $r = scalar( @array ) - 2; my $k = 0; for( my $i = 0; $i <= $r ; $i = $i + 2 ) { if( $array[ $i ] < $array[ $i + 1 ] ) { $min_cand[ $k ] = $array[ $i ]; $max_cand[ $k ] = $array[ $i + 1 ]; } else { $min_cand[ $k ] = $array[ $i + 1 ]; $max_cand[ $k ] = $array[ $i ]; } ++$k; } if( scalar( @array ) % 2 != 0 ) { if( $min_cand[ 0 ] < $array[ $r + 1 ] ) { $max_cand[ $k ] = $array[ $r + 1 ]; } else { $min_cand[ $k ] = $array[ $r + 1 ]; } } my $m = $min_cand[ 0 ]; for( my $i = 1; $i < scalar( @min_cand ); ++$i ) { if( $min_cand[ $i ] < $m ) { $m = $min_cand[ $i ]; } } $result[ 0 ] = $m; $m = $max_cand[ 0 ]; for( my $i = 1; $i < scalar( @max_cand ); ++$i ) { if( $max_cand[ $i ] > $m ) { $m = $max_cand[ $i ]; } } $result[ 1 ] = $m; @result; } 1; __END__ # Below is stub documentation for your module. You better edit it!