LeetCode.637. 二叉树的层平均值

LeetCode.637. 二叉树的层平均值

难度：easy

BFS轻松写意

class Solution {
    public List averageOfLevels(TreeNode root) {
        List ansList = new ArrayList<>();
        Queue queue = new linkedList<>();
        if (root == null) {
            return ansList;
        }
        
        queue.offer(root);
        while (!queue.isEmpty()) {
            int size = queue.size();
            double sum = 0;
            for (int i = 0; i < size; i++) {
                TreeNode tmpNode = queue.poll();
                sum += (double)tmpNode.val;
                if (i == size - 1) {
                    ansList.add(sum / size);
                }
                if (tmpNode.left != null) {
                    queue.offer(tmpNode.left);
                }
                if (tmpNode.right != null) {
                    queue.offer(tmpNode.right);
                }
            }
        }
        return ansList;
    }
}