Update 32 20211102 binary tree.md

紀錄/32 20211102 binary tree.md

@@ -26,3 +26,54 @@ https://en.wikipedia.org/wiki/Binary_tree
 * 	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:
+
+列出跟 Binary Tree 相關的詞彙或術語:
+
+root, leaf, full tree, complete tree, null tree, rotate, balance tree in/pre/post/level-order
+(val, right, left)
+
+just jargons
+
+
+
+```typescript=
+// by Louis
+/** Iteration in TS */
+function preorderTraversal (root: TreeNode | null): number[] {
+    let results: number[] = [];
+    let rightNodeStack: TreeNode[] = [null];
+    let curr = root;
+    while (curr != null) {
+        results.push(curr.val);
+        if (curr.right != null) rightNodeStack.push(curr.right);
+        if (curr.left != null) curr = curr.left;
+        else curr = rightNodeStack.pop();
+    }
+
+    return results;
+}
+
+/** Recursion in TS */
+function preorderTraversal (root: TreeNode | null): number[] {
+    let results: number[] = [];
+    recursiveHelper(root);
+    return results;
+
+    function recursiveHelper (node: TreeNode){
+        if (node == null) return;
+        results.push(node.val);
+        recursiveHelper(node.left);
+        recursiveHelper(node.right);
+    }
+};
+
+```
+
+
+Post order:
+https://leetcode.com/problems/binary-tree-postorder-traversal/discuss/45551/Preorder-Inorder-and-Postorder-Iteratively-Summarization
+
+TODO: 不太懂Interactive在幹什麼，看有沒有辦法用比較易懂的方式講Interactive