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 [].
1 public class Solution {
2 public List<String> generatePossibleNextMoves(String s) {
3 List<String> res = new ArrayList<String>();
4 if (s==null || s.length()<=1) return res;
5 for (int i=0; i<s.length()-1; i++) {
6 if (s.charAt(i)=='+' &&s.charAt(i+1)=='+')
7 res.add(process(s, i));
8 }
9 return res;
10 }
11
12 public String process(String s, int i) {
13 StringBuffer result = new StringBuffer();
14 result.append(s.substring(0, i));
15 result.append("--");
16 result.append(s.substring(i+2));
17 return result.toString();
18 }
19 }
