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 

[]

.

周遊字元串，遇到兩個相鄰的‘+’就替換成‘-’，添加進結果中。代碼如下：

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.charAt(i) == '+' && s.charAt(i + 1) == '+') {
                res.add(new StringBuilder(s).replace(i, i + 2, "--").toString());
            }
        }
        return res;
    }
}