all the questions about binary trees

All the questions about binary trees:

1、   Scramble String (递归)
2、 Unique Binary Search Trees (DP)
3、 Unique Binary Search Trees II (递归)
4、 Binary Tree Inorder Traversal (递归或迭代)
5、 Validate Binary Search Tree (递归)
6、 Recover Binary Search Tree
7、 Same Tree (递归)
8、 Symmetric Tree (递归)
9、 Binary Tree Level Order Traversal (BFS)
10、 Binary Tree Zigzag Level Order (BFS)
11、 Maximum Depth of Binary Tree (递归)
12、 Construct Binary Tree from Preorder andInorder Traversal (递归)
13、 Construct Binary Tree from Inorder andPostorder Traversal (递归)
14、 Binary Tree Level Order Traversal II(BFS)
15、 Convert Sorted Array to Binary SearchTree (递归)
16、 Convert Sorted List to Binary Search Tree(递归)
17、 Balanced Binary Tree (递归)
18、 Minimum Depth of Binary Tree (迭代)
19、 Path Sum (递归)
20、 Path Sum II (递归)
21、 Flatten Binary Tree to Linked List (递归)
22、 Populating Next Right Pointers in EachNode
23、 Populating Next Right Pointers in Each NodeII
24、 Binary Tree Maximum Path Sum (递归)
25、 Sum Root to Leaf Numbers (递归)
26、 Binary Tree Preorder Traversal (递归或迭代)
27、Binary Tree Postorder Traversal (递归或迭代)

2、  Minimum depth of binary tree是迭代么？