Update and rename 339. Nested List Weight Sum.md to 339._Nested_List_Weight_Sum.md

Author: 0xkookoo

docs/Leetcode_Solutions/Python/339. Nested List Weight Sum.md

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+# 339. Nested List Weight Sum
+
+**<font color=red>难度: Easy</font>**
+
+## 刷题内容
+
+> 原题连接
+
+* https://leetcode.com/problems/nested-list-weight-sum/description/
+
+> 内容描述
+
+```
+Given a nested list of integers, return the sum of all integers in the list weighted by their depth.
+
+Each element is either an integer, or a list -- whose elements may also be integers or other lists.
+
+Example 1:
+
+Input: [[1,1],2,[1,1]]
+Output: 10 
+Explanation: Four 1's at depth 2, one 2 at depth 1.
+Example 2:
+
+Input: [1,[4,[6]]]
+Output: 27 
+Explanation: One 1 at depth 1, one 4 at depth 2, and one 6 at depth 3; 1 + 4*2 + 6*3 = 27.
+```
+
+## 解题方案
+
+> 思路 1
+******- 时间复杂度: O(N)******- 空间复杂度: O(1)******
+
+很简单的递归
+
+假设nestedList铺平开来，里面一共有N个NestedInteger的话，时间复杂度就是O(N)
+```python
+class Solution:
+    def depthSum(self, nestedList):
+        """
+        :type nestedList: List[NestedInteger]
+        :rtype: int
+        """
+        def helper(nestedList, depth):
+            res = 0
+            for nested in nestedList:
+                if nested.isInteger():
+                    res += depth * nested.getInteger()
+                else:
+                    res += helper(nested.getList(), depth+1)
+            return res
+        return helper(nestedList, 1)
+```