Leetcode 刷题

剑指 Offer 32 - II. 从上到下打印二叉树 II

  • 难度:中等

/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public List<List<Integer>> levelOrder(TreeNode root) {
Queue<TreeNode> queue = new LinkedList<> ();
List<List<Integer>> res = new ArrayList<>();
if(root != null){
queue.add(root);
}

while(!queue.isEmpty()){
List<Integer> tmp = new ArrayList<> ();
for(int i = queue.size(); i > 0; i--){
TreeNode node = queue.poll();
tmp.add(node.val);
if(node.left != null) queue.add(node.left);
if(node.right != null) queue.add(node.right);
}
res.add(tmp);
}
return res;
}
}