LeetCode 464 Can I Win - Walkthrough

Pool of integers $1$ to $n$. Players pick unused numbers. First to reach sum $\geq target$ wins. Can Player 1 guarantee a win? State: bitmask of used numbers. $dp[mask]$ = true if current player can win from this state. Example: $n=4$, $target=6$. From empty mask, try $1$, 2, 3, or 4.

If taking 4 doesn't win immediately, check if opponent loses from resulting mask. Current sum is computed from mask. If $sum + pick \geq target$, current player wins. Else, recurse and check if any pick leads to opponent's loss.