A= [1 2 3 ; 2 4 8 ; -1 2 -2]
sz = size(A);  % Input handling
n = sz(1);
L = zeros(n,n);

p = 1:n;
for i = 1:n-1
    [maxel, pos] = max(abs(A(i:n,i)));
    s = pos+i-1;
    p([i s]) = p([s, i]);
    A([i s],:) = A([s, i],:);
    L([i s],:) = L([s, i],:);
    if A(i,i) ~=0
       A(i+1:n, i+1:n) = A(i+1:n, i+1:n) - A(i+1:n,i)/A(i,i) * A(i, i+1:n)
    end
end

I = eye(n,n);
PM = I(p,:);    % Construct permutation matrix
triu(A)         % Print upper triangular part of A