Permutations II — LeetCode 47 Python Solution
MediumArrayBacktrackingSorting
- Problem
- #47
- Pattern
- Backtracking
- Reading time
- 4 min
- Source
- leetcode.com
The problem
Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order.
Example
- Input
- nums = [1,1,2]
- Output
- [[1,1,2],
Python solution
Python
class Solution:
def permuteUnique(self, nums: List[int]) -> List[List[int]]:
def dfs(i: int):
if i == n:
ans.append(t[:])
return
for j in range(n):
if vis[j] or (j and nums[j] == nums[j - 1] and not vis[j - 1]):
continue
t[i] = nums[j]
vis[j] = True
dfs(i + 1)
vis[j] = False
n = len(nums)
nums.sort()
ans = []
t = [0] * n
vis = [False] * n
dfs(0)
return ansComplexity
| Measure | Complexity |
|---|---|
| Time | O(n \times n!) |
| Space | O(n) auxiliary |
Pattern: Backtracking
Build candidates one choice at a time and abandon a branch the moment it cannot work. LeetCode 47. Permutations II is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Backtracking.
The backtracking guide has the Python template for the pattern and the 105 LeetCode problems that use it.
Related problems
Frequently asked questions
- How hard is LeetCode 47. Permutations II?
- LeetCode 47. Permutations II is rated Medium on LeetCode.
- What is the time complexity of LeetCode 47. Permutations II?
- The Python solution on this page runs in O(n \times n!).
- What is the space complexity of LeetCode 47. Permutations II?
- The Python solution on this page uses O(n) auxiliary space.
- What topics does LeetCode 47. Permutations II cover?
- LeetCode 47. Permutations II is tagged Array, Backtracking and Sorting on LeetCode.