function f = DCS(x,y,x0)
syms t;

if(length(x) == length(y))
    n = length(x);
    c(1:n) = 0.0;
else
    disp('x和y的維數不相等！');
    return;
end

c(1) = y(1);
for(i=1:n-1)   
    for(j=i+1:n)
        y1(j) = (x(j)-x(i))/(y(j)-y(i));
    end
    c(i+1) = y1(i+1);     
    y = y1;   
end

f = c(n);
for(i=1:n-1)
    f = c(n-i) + (t-x(n-i))/f;
    f = vpa(f,6);
    if(i==n-1)
        if(nargin == 3)
            f = subs(f,'t',x0);
        else
            f = vpa(f,6);
        end
    end
end;