Knapsack Variant Ac2D11
1. **Problem Statement:** We have a variant of the 0-1 knapsack problem where each item $a_i$ can be rejected, fully accepted, or half-accepted. The capacity is $S$, and $V(T,m)$ is the optimal profit for the first $m$ items with capacity $T$.
2. **Key Definitions:**
- $v_i$: value of item $i$
- $s_i$: size of item $i$
- Half-accepting means taking half the size and half the value.
3. **Recurrence Relation:**
The optimal profit $V(T,m)$ is the maximum of:
- Not taking item $m$: $V(T,m-1)$
- Taking full item $m$ if it fits: $V(T - s_m, m-1) + v_m$
- Taking half item $m$ if half fits: $V(T - \frac{s_m}{2}, m-1) + \frac{v_m}{2}$
4. **Check each option:**
- (a) uses min and subtracts $v_m$ and $v_m/2$ from $T$, which is incorrect because capacity reduces by size, not value, and we maximize profit, not minimize.
- (b) matches the correct recurrence: max, subtract sizes $s_m$ and $s_m/2$ from $T$, add values $v_m$ and $v_m/2$.
- (c) is a simplified version ignoring half-acceptance, but correct for classical 0-1 knapsack.
- (d) uses min instead of max, incorrect.
- (e) uses max but subtracts values $v_m$ from $T$, incorrect.
- (f) $V(T,1) = 0$ if $s_1 > T$ is correct: if the first item doesn't fit, profit is zero.
- (g) subtracts values $v_m$ from $T$, incorrect.
- (h) is false because some choices are correct.
- (i) $V(0,m) = 0$ is correct: zero capacity means zero profit.
5. **Final correct statements:** (b), (c), (f), and (i).
**Answer:**
$$
\boxed{\text{Correct: } b, c, f, i}
$$