Gauss- Seidel

function x = GaussSeidel(A,b,x0,tol,maxiter)
    [n n] = size(A)
    xc = zeros(n,1);
    xp = x0;
    W = 1;
    for k = 1 : maxiter
        for i = 1 : n
            ok = 1;
            s1=0;
            s2=0;
                for j = 1: i-1
                    s1 = s1 + A(i,j)*xc(j);
                endfor
                for j = i+1 : n
                    s2 = s2 + A(i,j)*xp(j);
                endfor

            xc(i) = (b(i) - s1 - s2)/A(i,i);
            if xc - xp < tol
                W = 0;
            endif
            xp = xc;
        endfor
        if W = 0
            break;
        endif
    endfor
    x = xc;
endfunction