leetcode1047

 1 class Solution:
 2     def removeDuplicates(self, S: str) -> str:
 3         l = []
 4         for i in range(len(S)):
 5             s = S[i]
 6             if len(l) == 0:
 7                 l.append(s)
 8             else:
 9                 top = l[-1]
10                 if s == top:
11                     l.pop(-1)
12                 else:
13                     l.append(s)
14         result = ''
15         for i in range(len(l)):
16             result += l[i]
17         return result