Merge pull request #982 from tlylt/fix-77-python

fix Qn0077 Python indent

problems/0077.组合.md

@@ -422,13 +422,13 @@ class Solution:
         def backtrack(n,k,startIndex):
             if len(path) == k:
                 res.append(path[:])
-            return 
+                return
             for i in range(startIndex,n - (k - len(path)) + 2):  #优化的地方
                 path.append(i)  #处理节点 
                 backtrack(n,k,i+1)  #递归
                 path.pop()  #回溯，撤销处理的节点
-    backtrack(n,k,1)
-    return res
+        backtrack(n,k,1)
+        return res
 ```