144. Binary Tree Preorder Traversal - Easy
문제
Given the root of a binary tree, return the preorder traversal of its nodes’ values.
제한사항
- The number of nodes in the tree is in the range [0, 100].
- -100 <= Node.val <= 100
입출력 예
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Example 1:
Input: root = [1,null,2,3]
Output: [1,2,3]
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Example 2:
Input: root = []
Output: []
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Example 3:
Input: root = [1]
Output: [1]
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Example 4:
Input: root = [1,2]
Output: [1,2]
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Example 5:
Input: root = [1,null,2]
Output: [1,2]
풀이
- Tree
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/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func preorderTraversal(root *TreeNode) []int {
if (root == nil) {
return []int{}
}
var res []int
res = append(res, root.Val)
left := preorderTraversal(root.Left)
if (len(left) != 0) {
res = append(res, left...)
}
right := preorderTraversal(root.Right)
if (len(right) != 0) {
res = append(res, right...)
}
return res
}