#P10737. Binary String Flipping Game
Binary String Flipping Game
Binary String Flipping Game
Alice and Bob play a turn‐based game on a binary string s. At the start, you are given the string s.
On each turn, the current player must choose a substring t of s such that t is exactly one of the following:
- $10$
- $100$
- $110$
- $1010$
Then, the player flips every digit of t (i.e. replaces every 1
with 0
, and every 0
with 1
). For example, $100$ becomes $001$ after flipping.
A move is only allowed if it does not cause the mover to eventually face a losing position — in other words, both players play optimally and will avoid moves that would immediately turn the game into a loss for themselves.
If a player has no valid moves on their turn, they lose. Alice moves first. Determine which player will win under optimal play.
inputFormat
The input consists of a single line containing a binary string s (i.e. a string consisting only of characters 0
and 1
). It is guaranteed that the length of s is relatively small so that a complete search is feasible.
outputFormat
Output a single line containing Alice
if Alice can force a win under optimal play, and Bob
otherwise.
sample
10
Alice