Execise 6.1

[RangerChu]

V_t denote the array of state values used at time t in the TD error (6.5) and in the TD update (6.2).
And delta_t is calculated at time t+1.

The agent only updates the V value of S_t at the time of t+1, and the V values of other states remain unchanged.

[ehddnr747]

You misunderstand the problem definition.
Even though delta_t is calculated at time step t+1 with R_[t+1] and S_[t+1], use call it V_t, which is used to calculate delta_t.

[zexiangliu]

I agree with @ehddnr747 that V_t is used to calculate delta_t instead of V_{t+1}. If that is fixed in @RangerChu 's answer, we should have a correct solution.