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Solution: Flip Game

Explore how to apply backtracking to solve the Flip Game by scanning a string for consecutive plus signs and generating all possible next valid states after flipping them. Understand the algorithm's time and space complexity and learn to systematically enumerate all moves without modifying the original string in-place.

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:

  • 11 \leq currentState.length 500\leq 500

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

Solution

The main idea is to generate all possible valid next moves by ...