Merge pull request #838 from casnz1601/patch-15

Update 0078.子集.md

problems/0078.子集.md

@@ -207,17 +207,28 @@ class Solution {
 ## Python 
 ```python3
 class Solution:
+    def __init__(self):
+        self.path: List[int] = []
+        self.paths: List[List[int]] = []
+
     def subsets(self, nums: List[int]) -> List[List[int]]:
-        res = []  
+        self.paths.clear()
-        path = []  
+        self.path.clear()
-        def backtrack(nums,startIndex):
+        self.backtracking(nums, 0)
-            res.append(path[:])  #收集子集，要放在终止添加的上面，否则会漏掉自己
+        return self.paths
-            for i in range(startIndex,len(nums)):  #当startIndex已经大于数组的长度了，就终止了，for循环本来也结束了，所以不需要终止条件
+
-                path.append(nums[i])
+    def backtracking(self, nums: List[int], start_index: int) -> None:
-                backtrack(nums,i+1)  #递归
+        # 收集子集，要先于终止判断
-                path.pop()  #回溯
+        self.paths.append(self.path[:])
-        backtrack(nums,0)
+        # Base Case
-        return res
+        if start_index == len(nums):
+            return
+
+        # 单层递归逻辑
+        for i in range(start_index, len(nums)):
+            self.path.append(nums[i])
+            self.backtracking(nums, i+1)
+            self.path.pop()     # 回溯
 ```
 
 ## Go