Which part is incorrect?

function [indices] = kWeakestRows(mat,k)% function 
    disp("The number of soldiers in each row is:")
    answer = [];
    for i = 1:length(mat)
        fprintf("- Row %d: %d\n",i,sum(mat(i,:)));
        answer(end + 1,:) = [sum(mat(i,:)),i];
        end
    answer = sortrows(answer,1);
    indices = []; 
    for i = 1:k 
        indices(end + 1) = answer(i,2);
    end
    fprintf("The rows ordered from weakest to strongest are ");
    disp(indices);
end

[Ghazwan]

can you explain more?

Answer 1

[Hiro Yoshino]

I would do this much more simply:

mat = [1,1,0,0,0;
       1,1,1,1,0;
       1,0,0,0,0;
       1,1,0,0,0;
       1,1,1,1,1];

% sum in row direction
answer = sum(mat,2)

answer = 5×1

2 4 1 2 5

% sort and obtain the indices
[sMat, idx] = sort(answer,"ascend");
disp("The rows ordered from weakest to strongest are")

The rows ordered from weakest to strongest are

idx

idx = 5×1

3 1 4 2 5

If you want to extract first k then:

k = 3;
idx(1:k)

ans = 3×1

3 1 4