Create all combination of strings

Question

Celso Mauro Nhanga Dos Santos 2021-3-6

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/764531-create-all-combination-of-strings

评论： per isakson 2021-3-7

Hello guys,

I need to create a matrix permutation with value from P1:P8. I tried to use the following code:

Pat = sym('p', [1 8]);

pn = nchoosek([Pat],5);

Str = string(pn)

"p1" "p2" "p3" "p4" "p5"

"p1" "p2" "p3" "p4" "p6"

"p1" "p2" "p3" "p5" "p6"

"p1" "p2" "p4" "p5" "p6"

"p1" "p3" "p4" "p5" "p6"

"p2" "p3" "p4" "p5" "p6"

"p1" "p2" "p3" "p4" "p7" ...

The code worked; nevertheles, it gave me only all possible combinations instead of all permutations. Next I tried this following code:

x = sym('p', [1 8]);

K = 5;

C = cell(K, 1);

[C{:}] = ndgrid(x);

y = cellfun(@(x){x(:)}, C);

y = [y{:}];

But the thing is that this code seems a lot for my computer to handle. So would like your help to see if I can generate all permitation of the string P1:P8.

Thank you in advance

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Answer 1

per isakson 2021-3-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/764531-create-all-combination-of-strings#answer_640451

编辑：per isakson 2021-3-7

在 MATLAB Online 中打开

See: perms, All possible permutations

In response to comment

Does the function, cssm(), do what you ask for?

>> all_permutations = cssm( 3, 2 )
all_permutations = 
  6×2 string array
    "p2"    "p1"
    "p1"    "p2"
    "p3"    "p1"
    "p1"    "p3"
    "p3"    "p2"
    "p2"    "p3"
>> 

where

function    all_permutations = cssm( n, k )
    str = arrayfun( @(jj) "p"+jj, (1:n) );
    % or shorter str="p"+(1:n);
    all_combinations = nchoosek( str, k );
    %
    ix  = 1;
    fac = factorial( k );
    all_permutations = strings( size(all_combinations,1)*fac, k );
    for combination = permute( all_combinations, [2,1] )
        all_permutations( 1+(ix-1)*fac : ix*fac, : ) = perms( combination );
        ix = ix + 1;
    end
    %
    test = unique( all_permutations, 'rows' );    
    assert( all( size(test) == size(all_permutations) ) );
end