How to define heat flux boundary condition for 1D transient heat conduction analysis?

L = 0.2*10^-3; %m, wall thickness
n = 5; %number of nodes
T0 = 300; %deg K, initial temperature of wall
dx = L/n; %m node thickness
alpha = 1.13*10^-4; %thermal diffusivity
t_final = 12*10^-3; %s, final time 
dt = 1.1*10^-5; %time step, %s
q = 0.4*1.12*10^10; % heat flux (W/m^2)
rho = 8940; % density of material (kg/m^3)
C = 386; %specific heat capacity (J/kg K)

x = dx/2:dx:L-dx/2;

T = ones(n,1)*T0;

dTdt = zeros(n,1);

t = 0:dt:t_final;

for j = 1:length(t)
    for i = 2:n-1
        dTdt(i) = alpha*(-(T(i)-T(i-1))/dx^2+(T(i+1)-T(i))/dx^2);
    end
    dTdt(1) = alpha*((T(1)-T0)/(dx))+ (q/(rho*C));

Here is it the right way to define heat flux boundary condition ?

    dTdt(n) = alpha*((T0-T(n-1))/(2*dx));
    T = T+dTdt*dt;
    figure(1)
    plot(x,T)
end