Merge remote-tracking branch 'origin/master'

python-leetcode/README.md

@@ -20,5 +20,8 @@
 6. [二叉树的层次遍历](./solution/tree/leetcode_32_.py)
 7. [递增顺序查找二叉树](./solution/tree/leetcode_897_.py)
 8. [单值二叉树](./solution/tree/leetcode_965_.py)
+9. [二叉树的层次遍历II](./solution/tree/leetcode_107_.py)
+10. [二叉树层的平均值](./solution/tree/leetcode_637_.py)
+
 
 

python-leetcode/solution/tree/leetcode_107_.py

+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# coding=utf-8
+"""
+107. 二叉树的层次遍历II
+"""
+from solution import TreeNode
+
+
+class Solution:
+    def levelOrderBottom(self, root: TreeNode) -> List[List[int]]:
+        res = []
+
+        def helper(root: TreeNode, k: int):
+            if not root:
+                return
+            if len(res) <= k:
+                res.append([])
+            res[k].append(root.val)
+            helper(root.left, k + 1)
+            helper(root.right, k + 1)
+
+        helper(root, 0)
+        return res[::-1]

python-leetcode/solution/tree/leetcode_637_.py

+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# coding=utf-8
+"""
+637. 二叉树的层平均值
+"""
+from solution import TreeNode
+
+
+class Solution:
+    def averageOfLevels(self, root: TreeNode) -> List[float]:
+        res = []
+        average=[]
+
+        def helper(root: TreeNode, k: int):
+            if not root:
+                return
+            if len(res) <= k:
+                res.append([])
+            res[k].append(root.val)
+            helper(root.left, k + 1)
+            helper(root.right, k + 1)
+
+        helper(root, 0)
+        for li in res:
+            average.append(sum(li)/len(li))
+        return average