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 [].

遍历字符串，遇到两个相邻的‘+’就替换成‘-’，添加进结果中。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.charAt(i) == '+' && s.charAt(i + 1) == '+') {                res.add(new StringBuilder(s).replace(i, i + 2, "--").toString());            }        }        return res;    }}