# 293-flip-game

## Question

https://leetcode.com/problems/flip-game/description/

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.

Example:

``````given s = "++++", after one move, it may become one of the following states:

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

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

## Thought Process

1. Check Character Pair
1. Starting from index 1, we need to make sure the current character and previous character are both '+'
2. We flip and add the result to the list, then reset
3. Time complexity O(n)
4. Space complexity O(1)

## Solution

``````class Solution {
public List<String> generatePossibleNextMoves(String s) {
List<String> res = new ArrayList<>();
char[] path = s.toCharArray();
for (int i = 1; i < path.length; i++) {
if (path[i - 1] == '+' && path[i] == '+') {
path[i - 1] = path[i] = '-';