Flip Game

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:

[
  "--++",
  "+--+",
  "++--"
]

思路：就是记录每个状态，记得翻转回来，然后再继续即可。

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {
        List<String> list = new ArrayList<String>();
        if(s == null || s.length() == 0) return list;
        char[] chars = s.toCharArray();
        for(int i=0; i<chars.length-1; i++){
            if(chars[i]=='+' && chars[i+1]=='+'){
                chars[i] = '-';
                chars[i+1] = '-';
                list.add(new String(chars));
                chars[i] = '+';
                chars[i+1] = '+';
            }
        }
        return list;
    }
}