how to make the numbers on the matrix with alternative sign?

I want to create a matrix that the main diagonal of K are alternatively 2 and -2’s, the sub- and sup-diagonal of K alternatively 1 and -1’s, and everywhere else 0. The size of K is 2n by 2n.

Here is what I got so far.

x=ones(1,5);
y=ones(1,4);
x2=2*x;
y2=y*-1;
z=diag(x2,0)
[rows, columns] = size(z)

z(1:2*rows+2:end) = -z(1:2*rows+2:end)

b=diag(y2,+1)

d=diag(y2,-1)
g=z+b+d