Exhaustively permutate a vector of size 20

Question

Rayne 2016-4-9

0
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https://ww2.mathworks.cn/matlabcentral/answers/278094-exhaustively-permutate-a-vector-of-size-20

回答： Walter Roberson 2016-4-9

采纳的回答： Walter Roberson

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Hi,

I'm trying to exhaustively permutate a vector of size 20, but when I tried to use perms(v), I get the error

Error using perms (line 23)
Maximum variable size allowed by the program is exceeded.

I've read from the documentation that the memory required for vectors longer than 10 is astronomical. So I'm looking for an alternative.

What I'm trying to do is the following (using a smaller scale example, where the vector here is only of size 3 instead of 20) - find all vectors, x, of length 3 where (x_i)^2 = 1, e.g.

(1, 1, 1), 
(-1, 1, 1), (1, -1, 1), (1, 1, -1),
(-1, -1, 1), (-1, 1, -1), (1, -1, -1),
(-1, -1, -1)

I was trying to iteratively create the "base vector", where the number of '-1' elements increased from 0 to 20, then use perms(v) to permutate each "base vector", but I ran into the memory problem.

Is there any alternative to do this?

Thank you.