Creating possible addition of a number
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fyza affandi
il 24 Feb 2019
Commentato: fyza affandi
il 24 Feb 2019
I have a set of array A
A= [1 2 4 8 16]
For example I want a set of number that make up total of 4 (from A), it would be
B=[1 1 1 1] *total in array B would be 4*
B=[1 1 2]
B=[2 2]
B=[4]
Is it possible to do it in Matlab?
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John D'Errico
il 24 Feb 2019
Modificato: John D'Errico
il 24 Feb 2019
Trivial, if you download my partitions function from the File Exchange.
A = [1 2 4 8 16];
partitions(4,A)
ans =
4 0 0 0 0
2 1 0 0 0
0 2 0 0 0
0 0 1 0 0
Each row of the result tells you how many times that element appears in the target sum.
Find it here:
Note that the number of such partitions can be immense for some problems. You can easily overwhelm such a tool. For example, I have another utiility that will count the number of partitions of an integer.
numberOfPartitions(1000)
ans =
24061467864032622473692149727991
Thus as the sum of numbers in the set [1:1000]. It gets big, and does so pretty fast.
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Più risposte (1)
Stephen23
il 24 Feb 2019
Download John D'Errico's excellent partitions:
and use it like this:
>> A = [1,2,4,8,16];
>> M = partitions(4,A);
>> F = @(v)repelem(A,v);
>> C = cellfun(F,num2cell(M,2),'uni',0);
>> C{:}
ans =
1 1 1 1
ans =
1 1 2
ans =
2 2
ans =
4
2 Commenti
John D'Errico
il 24 Feb 2019
One of the things I should have added as an option, was the ability to return the partitions in an expanded form, something much like Stephen did here. You can never have too many options in an interface. Well, at least not until you do. ;-)
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