Merge pull request #1702 from tlylt/update-0090

Update problems/0090.子集II.md

problems/0090.子集II.md

@@ -262,6 +262,8 @@ class Solution:
 ```
 
 ### Python3
+
+不使用used数组
 ```python3
 class Solution:
     def subsetsWithDup(self, nums: List[int]) -> List[List[int]]:
@@ -288,6 +290,28 @@ class Solution:
         return res
 ```
 
+使用used数组
+```python3
+class Solution:
+    def subsetsWithDup(self, nums: List[int]) -> List[List[int]]:
+        result = []
+        path = []
+        nums.sort()
+        used = [0] * len(nums)
+        def backtrack(nums, startIdx):
+            result.append(path[:])
+            for i in range(startIdx, len(nums)):
+                if i > startIdx and nums[i] == nums[i-1] and used[i-1] == 0:
+                    continue
+                used[i] = 1
+                path.append(nums[i])
+                backtrack(nums, i+1)
+                path.pop()
+                used[i] = 0
+        backtrack(nums, 0)
+        return result
+```
+
 ### Go 
 
 ```Go
@@ -526,7 +550,7 @@ func subsetsWithDup(_ nums: [Int]) -> [[Int]] {
 
 ### Scala
 
-不使用userd数组:
+不使用used数组:
 
 ```scala
 object Solution {