66: Binary tree preorder traversal

Given a binary tree, return preorder traversal of the tree

Note: write the iterative solution, the recursive solution is trivial (see below)

public void PreorderTraversal(TreeNode root)
{
    if (root == null)
    {
        return;
    }
    Console.WriteLine(root.Value);
    PreorderTraversal(root.Left);
    PreorderTraversal(root.Right);
}

 

Example 1

Input:     1   
          / \  
         5   3 

Output: [1, 5, 3]

Example 2

Input:     1   
            \  
             3 

Output: [1, 3]