Arranging an array so that duplicates will turn up first

[ashimk1]

Hi All,

I have an array that contains duplicates as well unique numbers.
ex- (21, 33, 35, 21, 33, 70, 33, 35, 50)

I need to arrange it in such a way that all the duplicates will come up first followed by unique numbers.

Result for the given example should be:
(21, 21, 33, 33, 35, 35, 70, 50)

This a trivial problem in C, creating a binary search tree from the array solves the problem.

As I am new to Perl I don't know indepth of the language.
Would appreciate any help on this regard.

~Ashim

[KevinADC]

Hi All,

I have an array that contains duplicates as well unique numbers.
ex- (21, 33, 35, 21, 33, 70, 33, 35, 50)

I need to arrange it in such a way that all the duplicates will come up first followed by unique numbers.

Result for the given example should be:
(21, 21, 33, 33, 35, 35, 70, 50)

This a trivial problem in C, creating a binary search tree from the array solves the problem.

As I am new to Perl I don't know indepth of the language.
Would appreciate any help on this regard.


~Ashim

All you have to do is sort the array numerically.

@sorted_list = sort {$a <=> $b} @unsoted_list;

See the sort() man page for details or the "Sorting Data with Perl - Part One" article in the Howto section of this website.

[KevinADC]

On second look, I think I misunderstood your requirements. The sample data will sort as needed just by sorting it numerically, but real data probably will not. A hash of arrays would work.

[nithinpes]

Ashim,
You can try the following script:

use strict;
use warnings;
 
my @final; my @duplicates; my @single;
my %hash=();
my @a=(11,34,55,67,88,101,97,88,11,11,34,83,101,67); ##your array
 
foreach(@a)
{
 
  if(exists $hash{$_})   ##check if the element was processed before
  { 
     push @{$hash{$_}},$_ ; 
  } 
 else {
  $hash{$_}= [$_];
}    
}
 
foreach(keys %hash) {
if(@{$hash{$_}}>1) {
push @duplicates,@{$hash{$_}}; ##take duplicates into this array
}
 else {
push @single,@{$hash{$_}}; ##take single elements in this array
}
}
@final = sort {$a <=> $b} @duplicates;
push @final,@single;
 
###Result #####
print "$_\t" foreach(@final);