637. Average of Levels in Binary Tree

문제

https://leetcode.com/problems/average-of-levels-in-binary-tree/description/

풀이

class Solution {
    List<Double> list = new ArrayList<>();
    public List<Double> averageOfLevels(TreeNode root) {
        if(root == null) {
            return list;
        }

        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        while(!queue.isEmpty()) {
            int size = queue.size();
            double sum = 0;
            for(int i = 0; i < size; i++) {
                TreeNode node = queue.poll();
                sum += node.val;
                if(node.left != null) {
                    queue.add(node.left);
                }
                if(node.right != null) {
                    queue.add(node.right);
                }
            }
            list.add(sum/size);
        }

        return list;
    }
}