Click here to go back to LeetCode summary page.
Problem description is here, or as follows:
Given a binary tree, return the preorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [1,2,3]. Note: Recursive solution is trivial, could you do it iteratively?
The definition of preorder traversal is illustrated as follows:
Comments on Solution 1, 2 and 3 are very similar to those in “Binary Tree Inorder Traversal” problem. See how Solution 2 here is different from the Solution 2 of “Binary Tree Inorder Traversal” and “Binary Tree Postorder Traversal” problems.
Again, Solution 1 and 2 should be memorized.