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.
class Solution(object):
def generatePossibleNextMoves(self, s):
"""
:type s: str
:rtype: List[str]
"""
if not s: return []
res = []
for i in range(1,len(s)):
if s[i-1:i+1]=='++':
s1 = s[:i-1]+'--'+s[i+1:]
res.append(s1)
return res
1 注意res.append(s1)要和s1 = s[:i-1]+'--'+s[i+1:]在同一个缩进上，不然就会出现没有定义就调用的错误
2 比如当没有‘++’满足题意，那就直接走res.append(s1)这句，就会出现没有定义就调用的错误
3 不能写成s[i-1:i+1]='--'这种赋值形式，没有这样的赋值，只能通过s1 = s[:i-1]+'--'+s[i+1:]来构建