293. 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:

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

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

 此题比较简单，代码如下：

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {
        List<String> res = new ArrayList<String>();
        for(int i=0;i<s.length()-1;i++){
            if(s.startsWith("++",i)){
                String t = s.substring(0,i)+"--"+s.substring(i+2);
                res.add(t);
            }
        }
        return res;
    }
}