Merge pull request #1040 from leeeeeeewii/linkedlist

添加链表理论基础 python go版本

problems/链表理论基础.md

@@ -195,10 +195,20 @@ class ListNode {
 ```
 
 Python：
-
+```python
+class ListNode:
+    def __init__(self, val, next=None):
+        self.val = val
+        self.next = next
+```
 
 Go：
-
+```go
+type ListNode struct {
+    Val int
+    Next *ListNode
+}
+```