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 [].
Solution：
思路： str中向后找"++" 替换 加到结果
Time Complexity: O(N) Space Complexity: O(1)
Solution Code：
class Solution {
public List<String> generatePossibleNextMoves(String s) {
List<String> result = new ArrayList<>();
int i = -1;
while((i = s.indexOf("++", i + 1)) >= 0) {
result.add(s.substring(0, i) + "--" + s.substring(i + 2));
}
return result;
}
}
