131. Binary Tree Preorder Traversal

EasyTree

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

Examples

Input: [1,null,2,3]

Output: [1,2,3]

Explanation: Preorder: node, left, right.

Constraints

  • The number of nodes in the tree is in the range [0, 100].
  • -100 <= Node.val <= 100
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