DAY15P3.md

Binary Tree Right Side View

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• Question:

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.

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• Example:

Input: root = [1,2,3,null,5,null,4]

Output: [1,3,4]

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• Solution:

Code :

public class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        List<Integer> rst = new ArrayList<>();
        if(root == null) return rst;
        
        queue.offer(root);
        while(!queue.isEmpty()){
            int levelNum = queue.size();
            for(int i = 0; i < levelNum; i++){
                if(queue.peek().left != null) queue.offer(queue.peek().left);
                if(queue.peek().right != null) queue.offer(queue.peek().right);
                if(i == levelNum - 1) rst.add(queue.poll().val);
                else queue.poll();
            }
        }
        return rst;
    }
}