pull down to refresh

Well you are right to approach it game theoretically, but the answer should depend on N actually...
Ok thanks, for the hint.
Data for the first several N values: N | Optimal Move | Position Type 0 | can't move | Losing 1 | can't move | Losing 2 | 1 | Winning 3 | 2 | Winning 4 | 3 | Winning 5 | 1 | Winning 6 | 1 | Winning 7 | 2 | Winning 8 | 3 | Winning 9 | 1 | Winning 10 | 1 | Winning 11 | 2 | Winning 12 | 3 | Winning
Looking at winning positions:
For N = 2,3,4: take N-1 dumplings For N = 5,6,7: take (N-4) dumplings For N = 8,9,10: take (N-8) dumplings For N = 11,12,13: take (N-10) dumplings
Key observations:
The pattern repeats every 4 numbers For any N, we can find our position in the cycle using modulo 4 But we need to handle N = 0,1 as special cases
Therefore, if N ≥ 2:
Let k = N mod 4 If k = 1, take 1 If k = 2, take 2 If k = 3, take 3 If k = 0, take 3
Or more concisely, for N ≥ 2: optimal move = k if k ∈ {1,2,3} optimal move = 3 if k = 0 where k = N mod 4 For N < 2, no valid move exists.
This ensures you always force your opponents into a losing position eventually, while never breaking the etiquette rules.
reply
You're on the right track, but the solution is not quite accurate yet.
For example, if N=3, your solution says take 3. But that's rude because you take the last dumpling.
Another example, if N=5, your solution says take 1. But if N=5, you can take 3, then the next person will take 1, leaving the next person with the last dumpling. This maximizes your dumplings without being rude.
reply
Ah yes, how about this:
optimal_move = if N ≤ 2: invalid if N ≤ 4: N-1 if N mod 4 ∈ {1,3}: 2 if N mod 4 ∈ {0,2}: 3
reply