function lambda = powerMethod( A )
[n,~] = size(A);
iter_num = 500;
v_k = ones(n,1);
for i = 1:iter_num
    v_k1 = A * v_k;
    [~, index] = max(abs(v_k1));
    lambda = v_k1(index)/v_k(index);
    v_k = v_k1;
end
end

