90. Subsets II-array
题目分析：以每个位置后边的所有位置与当前位置拼接，事件复杂的是阶乘的
class Solution:
# @param num, a list of integer
# @return a list of lists of integer
# a dfs problem
def dfs(self, res, val, num, start):
if val not in res:
res.append(val)
for i in range(start, len(num)):
self.dfs(res, val+[num[i]], num, i+1)
def subsetsWithDup(self, S):
res = []
if len(S) == 0:
return res
S.sort()
val = []
self.dfs(res, val, S, 0)
return res