429. N 叉树的层序遍历

题目

代码

class Solution {
    public List<List<Integer>> levelOrder(Node root) {
        List<List<Integer>> res = new ArrayList<>();
        if (root == null) return res;//特判
        LinkedList<Node> queue = new LinkedList<>();
        queue.add(root);
        while (!queue.isEmpty()) {
            int size = queue.size();
            List<Integer> level = new ArrayList<>();
            for (int i = 0; i < size; i++) {
                Node node = queue.removeFirst();
                level.add(node.val);
                for (int j = 0; j < node.children.size(); j++) {
                    queue.add(node.children.get(j));
                }
            }
            res.add(level);
        }
        return res;
    }
}