How to avoid "doubling up" in a RNG?

Question

Connor K Riggs 2021-4-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/791927-how-to-avoid-doubling-up-in-a-rng

评论： the cyclist 2021-4-3

So, I've found a way to get my code to run 6 times through, but I've encountered a different problem. Since I'm using a random number generator to select which squares to turn the 0 to a 1, it's possible for my random number generator to select the same square twice. I want to ensure that the squares selected are unique. Once again, any help would be appreciated. EDIT: I have to use a for loop, not a while loop

x = zeros(10,10);
for i = 1:6
    m = randi(10)
    n = randi(10)
    if x(m,n) == 0
       x(m,n) = 1;
    elseif x(m,n) == 1
    end
end

3 个评论
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Connor K Riggs 2021-4-3

Unfortunately, I have to use a for loop, not a while loop.

David Fletcher 2021-4-3

编辑：David Fletcher 2021-4-3

在 MATLAB Online 中打开

Ahh, the vagaries of education. You could always break the for loop on the six ones condition, if only to highlight the asinine.

x = zeros(10,10);
for iter=1:inf
    m = randi(10)
    n = randi(10)
    x(m,n) = 1;
    if sum(x,'All')>5
        break
    end
end

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Answer 1

the cyclist 2021-4-3

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/791927-how-to-avoid-doubling-up-in-a-rng#answer_666247

在 MATLAB Online 中打开

Here is one way to do what I think you mean:

x = zeros(10,10);
% For M and N, select 6 random integers from 1:10.
M = randperm(10,6);
N = randperm(10,6);
for i = 1:6
    % Select each (m,n) in order from (M,N)
    m = M(i);
    n = N(i);
    if x(m,n) == 0
       GB(m,n) = 1;
    elseif x(m,n) == 1
    end
end

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Walter Roberson 2021-4-3

??

What is GB here?

The code you used cannot set two values in the same row (or the same column), so it does not need to do the test. However, the original homework seems to have the possibility that multiple values in the same row could occur.

the cyclist 2021-4-3

sigh

I'm guessing that @Connor K Riggs changed the code in their question. I copy/pasted the original, and did nothing other than change it so that there would be no repeated (m,n) values.

Caveat emptor my answer.

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