查找矩阵的大小，而无需在MATLAB中使用"size" [英] Find size of matrix, without using `size` in MATLAB

问题描述

假设我想查找矩阵的大小，但是不能使用任何功能，例如size，numel和length.有没有整齐的方法可以做到这一点?我可以想到一些使用循环的版本，例如以下版本，但是有可能在没有循环的情况下做到这一点?

Suppose I want to find the size of a matrix, but can't use any functions such as size, numel, and length. Are there any neat ways to do this? I can think of a few versions using loops, such as the one below, but is it possible to do this without loops?

function sz = find_size(m)
sz = [0, 0]
   for ii = m'    %' or m(1,:) (probably faster)
      sz(1) = sz(1) + 1;
   end

   for ii = m     %' or m(:,1)'
      sz(2) = sz(2) + 1;
   end    
end

根据记录:这不是一项作业，是出于好奇.尽管此问题的解决方案在这种情况下永远不会有用，但它们可能会在如何使用某些功能/技术方面提供新的知识.

And for the record: This is not a homework, it's out of curiosity. Although the solutions to this question would never be useful in this context, it is possible that they provide new knowledge in terms of how certain functions/techniques can be used.

推荐答案

这是更通用的解决方案

function sz = find_size(m)
sz = [];
m(f(end), f(end));
    function r = f(e)
        r=[];
        sz=[sz e];
    end
end

哪个

1. 适用于数组，单元格数组和对象数组
2. 它的时间复杂度是恒定的，并且与矩阵大小无关
3. 不使用任何MATLAB函数
4. 易于适应更高的尺寸

1. Works for arrays, cell arrays and arrays of objects
2. Its time complexity is constant and independent of matrix size
3. Does not use any MATLAB functions
4. Is easy to adapt to higher dimensions

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