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.
For example: Given the following binary tree,
1 <---
/ \
2 3 <---
\ \
5 4 <---
You should return [1, 3, 4].
Solution:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<Integer> rightSideView(TreeNode root) {
List<Integer> ans = new ArrayList<>();
if(root==null) return ans;
List<TreeNode> list = new ArrayList<>();
list.add(root);
while(!list.isEmpty()){
ans.add(list.get(list.size()-1).val);
List<TreeNode> tmp = new ArrayList<>();
for(int i=0; i<list.size(); i++){
TreeNode tn = list.get(i);
if(tn.left!=null) tmp.add(tn.left);
if(tn.right!=null) tmp.add(tn.right);
}
list = tmp;
}
return ans;
}
}