Given the root of 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 1:
Input: root = [1,2,3,null,5,null,4] Output: [1,3,4]
class Solution {
public List<Integer> rightSideView(TreeNode root) {
List<Integer> ans = new ArrayList<>();
if(root == null) return ans;
Queue<TreeNode> q = new LinkedList<>();
q.add(root);
while(!q.isEmpty()){
int size = q.size();
ans.add(q.peek().val);
for(int i = 0; i < size; i++){
TreeNode curr = q.poll();
if(curr.right != null){
q.add(curr.right);
}
if(curr.left != null){
q.add(curr.left);
}
}
}
return ans;
}
}