代码训练营第二十九天（Python）｜ 491.递增子序列 、46.全排列 、47.全排列 II

491.递增子序列

class Solution:
    def findSubsequences(self, nums: List[int]) -> List[List[int]]:
        res = []
        self.tracebacking(nums, 0, [], res)
        return res

    def tracebacking(self, nums, start, path, res):

        if len(path) >= 2:
            res.append(path[:])

        uset = set() # 用于本层去重
        for i in range(start, len(nums)):
            if nums[i] in uset or (path and path[-1] > nums[i]): # 同一层的相同元素，
                continue
            uset.add(nums[i])
            path.append(nums[i])
            self.tracebacking(nums, i+1, path, res)
            path.pop()

46.全排列

class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        res = []
        used = [False]*len(nums)
        self.tracebacking(nums, used, [], res)
        return res

    def tracebacking(self, nums, used, path, res):
        if len(path) == len(nums):
            res.append(path[:])
            return

        for i in range(len(nums)):
            if used[i]:
                continue
            path.append(nums[i])
            used[i] = True
            self.tracebacking(nums, used, path, res)
            path.pop()
            used[i] = False

47.全排列 II

class Solution:
    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        res = []
        nums.sort()
        used = [False]*len(nums)
        self.tracebacking(nums, used, [], res)
        return res

    def tracebacking(self, nums, used, path, res):
        if len(path) == len(nums):
            res.append(path[:])

        for i in range(len(nums)):
            if (i > 0 and nums[i] == nums[i-1] and not used[i-1]) or used[i]:
                continue
            path.append(nums[i])
            used[i] = True
            self.tracebacking(nums, used, path, res)
            path.pop()
            used[i] = False