Solution: Flip Game

Statement

You are playing a Flip Game with a friend.

You are given a string currentState consisting only of the characters '+' and '-'. Players take turns flipping two consecutive "++" into "--". The game ends when a player cannot make a move, at which point the other player wins.

Return all possible states of currentState after performing exactly one valid move. The answer may be returned in any order. If no valid move exists, return an empty list.

Constraints:

• $1 \leq$ currentState.length $\leq 500$

• currentState[i] is either '+' or '-'

Solution

The main idea is to generate all possible valid next moves by scanning the string for every occurrence of two consecutive '+' ...