Given a collection of numbers that might contain duplicates, return all possible unique permutations.
For example,[1,1,2] have the following unique permutations:
[ [1,1,2], [1,2,1], [2,1,1] ]
与上一题不同，就是在19行加个判断即可。
1 class Solution(object): 2 def __init__(self): 3 self.res = [] 4 5 def permuteUnique(self, nums): 6 """ 7 :type nums: List[int] 8 :rtype: List[List[int]] 9 """ 10 self.help(nums, 0, len(nums)) 11 12 return self.res 13 14 def help(self, a, lo, hi): 15 if(lo == hi): 16 self.res.append(a[0:hi]) 17 for i in range(lo, hi): 18 #判断 i 是否已经在当过头元素了 19 if a[i] not in a[lo:i]: 20 self.swap(a, i, lo) 21 self.help(a, lo + 1, hi) 22 self.swap(a, i, lo) 23 def swap(self, a, i, j): 24 temp = a[i] 25 a[i] = a[j] 26 a[j] = temp