Merge pull request #27 from programmingbookclub/35-2021-12-14-Binary-tree.md

Create 35 2021-12-14 Binary tree.md

Author: ytyubox

紀錄/35 2021-12-14 Binary tree.md

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+# LeetCode 讀書會第 35 次聚會 2021/12/14
+
+## leetcode 讀書會通知
+
+1. 項目: 第 35 次聚會
+2. 目的: 線上一起寫題目, 由有想法的人帶領, 先解題, 再看該題有趣的解法
+3. 時間: 12/14 (二) 20:00 ~ 21:00
+4. 地點: google meet 線上 (前 10 分鐘預備鏈接)
+5. 解題項目:  [Binary Tree](https://leetcode.com/explore/learn/card/data-structure-tree/)
+6. 共筆: GitHub https://github.com/programmingbookclub/Leetcode-club
+7. 備註: 
+
+當然這次要說到 3 題 MEDIUM！（立 Flag！） 116、117、236
+
+
+* 	MEDIUM	116	Populating Next Right Pointers in Each Node	https://leetcode.com/problems/populating-next-right-pointers-in-each-node
+* 	MEDIUM	117	Populating Next Right Pointers in Each Node II	https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii
+* 	MEDIUM	236	Lowest Common Ancestor of a Binary Tree	https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree
+* 	HARD	297	Serialize and Deserialize Binary Tree	https://leetcode.com/problems/serialize-and-deserialize-binary-tree
+
+--- 
+Notes:
+
+116: perfect binary tree
+1. using queue(level order) to travsal
+2. using 
+
+```swift=
+func connect(_ root: Node?,_ next: Node? = nil) -> Node? {
+    guard let root = root else {return nil}
+    root.next = next
+    connect(root.left, root.right)
+    connect(root.right, root.next?.left) 
+    return root
+}
+```
+
+117: 
+Discussion 的第一個，看起來跟 Solution 的這個解法相同
+https://leetcode.com/explore/learn/card/data-structure-tree/133/conclusion/1016/discuss/37828/O(1)-space-O(n)-complexity-Iterative-Solution
+
+
+236 swift with switch https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/discuss/1626458/Swift-with-switch