Binary Tree Preorder Traversal - LeetCode

最新推荐文章于 2024-05-30 07:40:02 发布

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本文介绍了一种实现二叉树前序遍历的方法，包括递归算法的具体实现细节。通过对二叉树节点的访问顺序进行定义，该文提供了一个清晰的解决方案，并附带了完整的Java代码示例。

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

For example:
Given binary tree {1,#,2,3},

return [1,2,3].

Note: Recursive solution is trivial, could you do it iteratively?

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    private ArrayList<Integer> result = new ArrayList<Integer>();
    public ArrayList<Integer> preorder(TreeNode root){
        if(root == null)
        return result;
        else {
            result.add(root.val);
            preorder(root.left);
            preorder(root.right);
            return result;
        }
    }
    public ArrayList<Integer> preorderTraversal(TreeNode root) {
        preorder(root);
        return result;
    }
}