Order is an issue, but formatting is not.
If all formatting is dropped, then your combinations would be:
1 2
1 3
1 4
2 3
2 4
3 4
But my desired output is:
1 2 3 4
1 3 2 4
1 4 2 3
All numbers are in each combination, with '1' always at first position.
kapil v < aaaaax2003%40yahoo.com">aaaaax2003
yahoo.com> wrote: I really don't ger what you are saying. The combinations I generated are what you asked for. Is the order and formatting of the output that is the issue ?
aditi gupta < aditi9783%40yahoo.co.in">aditi9783yahoo.co.in> wrote: Firstly, Thank you for replying.
Secondly,
Randal
'combine' does not do what I want, and I didn't understand the code enough to modify it. I need to find combinations of 1, 2, 3, 4 such that
combination 1: 1-2, 3-4
combination 2: 1-3, 2-4
combination 3: 1-4, 2-3
where a-b => a pairs with b.
This problem is Depth first search with backtracking, and my code isn't backtracking the right way. I searched for already available codes for this problem, and I found some pseudocodes, but that didn't help.
Maybe I need to search more.
Kapil
The code you wrote gives the following output (for 1, 2, 3, 4)
1,2
1,3
1,4
2,3
2,4
3,4
This is again a list of combinations different from what I have to generate.
I'm working on code, as well as searching for an already existing one. Any suggestions on where to search are most welcome.
Thanks!
Aditi
kapil v < aaaaax2003%40yahoo.com">aaaaax2003yahoo.com> wrote: A simple solution
#/usr/bin/perl -w
my array=(1,2,3,4,5,6,7);
combinations(array);
sub combinations{
my $array_ref=shift;
my array1 = {$array_ref};
$size=array1;
if($size<=1){return;}
$first=$array1[0];
for($i=1;$i<$size;$i++){
print "$first,$array1[$i]n";
}
shift(array1);
combinations(array1);
}
~
aditi gupta < aditi9783%40yahoo.co.in">aditi9783yahoo.co.in> wrote: Hello All:
I have an array of numbers, and I have to enumerate all possible combinations of pairs, without repetition of numbers or pairs in a particular combination.
For example: if array is list = (1, 2, 3, 4), then all possible combinations that could be generated are:
1-2, 3-4
1-3, 2-4
1-4, 2-3
For list = (1, 2, 3, 4, 5, 6), there are 15 possible combinations.
1-2, 3-4, 5-6; 1-2, 3-5, 4-6; 1-2, 3-6, 4-5
1-3, 2-4, 5-6; 1-3, 2-5, 4-6; 1-3, 2-6, 4-5... and so on.
1 always stays at the first position.
I was trying to do this in a recursive manner using a subroutine (my first subroutine!). The list is passed to it and result is stored in a 2D array (stem_pair).
=====subroutine======
sub enumerate
{
#array of numbers passed to sub
my list = _;
$flag = $list[0];
for (my $j = 1; $j<scalar(list); $j++)
{
# to initialize output array using flag
# since $flag = 1only during the 1st run of subroutine
if ($flag == 1 ) # block executed only once
{
push stem_pair, [ $list[0], $list[$j] ];
# first_pair: 1D array to keep track of pairs
# already added to stem_pair
first_pair = ($list[0], $list[$j] );
}
elsif (scalar(list) > 2) # if more than one pair remain in list
{
push first_pair ,$list[0];
push first_pair ,$list[$j];
# adding more pairs to the same row of stem_pair
push { $stem_pair[$#stem_pair] }, $list[0], $list[$j];
}
else # for last pair in the list
{
# adding more pairs to the same row of stem_pair
push { $stem_pair[$#stem_pair] }, $list[0], $list[$j];
}
temp = list;
# setting the zero value for elements just added to stem_pair
$temp[$j] = 0;
$temp[0] = 0;
# sorting array to get the two zeros as 1st and 2nd elements in array
new = sort(temp);
# deleting the two array elements
$a = shift(new);
$a = shift(new);
print "Remaining array is new, element deleted was $an";
# if no pairs are left
if (scalar(new) < 2){
for (my $k=0; $k < $j; $k++) # remove pairs from first_pair
{
$b = pop(first_pair);
$b = pop(first_pair);
}
# initialize new row in stem_pair
push stem_pair, [ first_pair];
}
# else, call the function with this new array new
else {enumerate(new);}
}
}
======END======
The code works fine for list= (1,2, 3, 4)
but gives extra repeated numbers for any list having more numbers.
For list = (1,2, 3, 4, 5, 6)
output:
1-2, 3-4, 5-6
1-2, 3-5, 4-6
1-2. 3-6., 4-5
1-2, 1-3, 2-4, 5-6 ### 1-2 should have been deleted before adding 1-3
### but my attempts to include more pop commands deleted
### 1-3 as well
1-2, 1-3, 2-5, 4-6
1-2, 1-3, 2-6, 4-5
1-2, 1-3, 1-4, 2-3, 5-6
1-2, 1-3, 1-4, 2-5, 3-6
1-2, 1-3, 1-4, 2-6, 3-5
1-2, 1-3, 1-4, 1-5, 2-3, 4-6
1-2, 1-3, 1-4, 1-5, 2-4, 3-6
1-2, 1-3, 1-4, 1-5, 2-6, 3-4
1-2, 1-3, 1-4, 1-5, 1-6, 2-3, 4-5
1-2, 1-3, 1-4, 1-5, 1-6, 2-4, 3-5
1-2, 1-3, 1-4, 1-5, 1-6, 2-5, 3-4
1-2, 1-3, 1-4, 1-5, 1-6 ### this is the final first_pair
### seen here as an extra 16th row
I've tried several things, but either am having less pairs (some pairs absent) or more pairs (some repetitions).
I would greatly appreciate any help / comments / suggestions.
Thank You!
Aditi
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