Binary Tree Preorder Traversal

Problem

• Given the root of a binary tree, return the preorder traversal of its nodes' values.

Reflections

Memorized at this point.

Go Solution

func preorderTraversal(root *TreeNode) []int {
    var res []int
    var dfs func(root *TreeNode) 
    dfs = func(root *TreeNode) {
        if root == nil {
            return 
        }

        res = append(res, root.Val)
        dfs(root.Left)
        dfs(root.Right)
    }

    dfs(root)

    return res
}

Performance

• Runtime beats: 100%
• Memory beats: 32%

Complexity

• Time: O(n)
• Space: O(n)