90. 子集 II

class Solution(object):
    def subsetsWithDup(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        def backtracking(path, start):
            res.append(path[:])
            for i in range(start, n):  # 递归的终止条件为start大于n时
                if nums[i] == nums[i - 1] and i > start:  # 这个条件和第40题的组合总和 II一样
                    continue
                else:
                    path.append(nums[i])
                    backtracking(path, i + 1)
                    path.pop()

        n = len(nums)
        nums = sorted(nums)
        res = []
        backtracking([], 0)
        return res