293 Flip Game

Problem:

You are playing the following Flip Game with your friend: Given a string that contains only these two characters: + and -, you and your friend take turns to flip two consecutive "++" into "--". The game ends when a person can no longer make a move and therefore the other person will be the winner.

Write a function to compute all possible states of the string after one valid move.

For example, given s = "++++", after one move, it may become one of the following states:

[ "--++", "+--+", "++--" ] If there is no valid move, return an empty list [].

Solutions:

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {
        List<String> result = new LinkedList<String>();
        StringBuilder sb = new StringBuilder(s);
        for (int i = 0; i < s.length() - 1; i ++) {
            if (s.charAt(i) == '+' && s.charAt(i + 1) == '+') {
                sb.setCharAt(i, '-');
                sb.setCharAt(i + 1, '-');
                result.add(sb.toString());
                sb.setCharAt(i, '+');
                sb.setCharAt(i + 1, '+');
            }
            
        }
        return result;
    }
}