Binary Tree Right Side View
Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
Example:
Input: [1,2,3,null,5,null,4]
Output: [1, 3, 4]
Explanation:
1 <---
/ \
2 3 <---
\ \
5 4 <---
Solution:
/**
* 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> result = new ArrayList<>();
int[] maxDepth = new int[]{1};
pre(root, result, 1, maxDepth);
return result;
}
private void pre(TreeNode root, List<Integer> result, int depth, int[] maxDepth) {
if (root == null) {
return;
}
if (depth >= maxDepth[0]) {
result.add(root.val);
}
maxDepth[0] = Math.max(maxDepth[0], depth + 1);
if (root.right != null) {
pre(root.right, result, depth + 1, maxDepth);
}
if (root.left != null) {
pre(root.left, result, depth + 1, maxDepth);
}
}
}