66. Binary Tree Preorder Traversal
Description
Given a binary tree, return the preorder traversal of its nodes' values.
Example
Given:
1
/ \
2 3
/ \
4 5
return [1,2,4,5,3].
Solution
import java.util.*;
/**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
*/
public class Solution {
/**
* @param root: A Tree
* @return: Preorder in ArrayList which contains node values.
*/
List<Integer> list = new ArrayList<Integer>();
public List<Integer> preorderTraversal(TreeNode root) {
if(root!=null){
list.add(root.val);
preorderTraversal(root.left);
preorderTraversal(root.right);
}
return list;
}
}