Leetcode75 199二叉树的右视图

199二叉树的右视图

给定一个二叉树的 根节点 root，想象自己站在它的右侧，按照从顶部到底部的顺序，返回从右侧所能看到的节点值。

示例 1:

输入: [1,2,3,null,5,null,4]
输出: [1,3,4]

示例 2:

输入: [1,null,3]
输出: [1,3]

示例 3:

输入: []
输出: []

提示:

• 二叉树的节点个数的范围是 [0,100]
• -100 <= Node.val <= 100

Solution 1

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        List<Integer> rightSideView = new ArrayList<>();
        traverse(root, rightSideView, 0);
        return rightSideView;
    }

    void traverse(TreeNode node, List<Integer> rightSideView, int depth) {
        if (node == null) {
            return;
        }
        // val
        if (depth >= rightSideView.size()) {
            rightSideView.add(node.val);
        }
        // R then L
        traverse(node.right, rightSideView, depth + 1);
        traverse(node.left, rightSideView, depth + 1);
    }
}