A = [ 1 -1  0  0;
     -1  2 -1  0;
      0 -1  2 -1;
      0  0 -1  2];
if all(eig(A) > 0)
    C = Alg10(A)
    C*C.' - A
    inv(C)
end

C =

     1     0     0     0
    -1     1     0     0
     0    -1     1     0
     0     0    -1     1


ans =

     0     0     0     0
     0     0     0     0
     0     0     0     0
     0     0     0     0


ans =

     1     0     0     0
     1     1     0     0
     1     1     1     0
     1     1     1     1