面试题32 – I. 从上到下打印二叉树

层次遍历，借助一个队列 
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector levelOrder(TreeNode* root) {
if(root==nullptr) return {};
queueq;
q.push(root);
vectorres;

while(!q.empty()){
TreeNode*temp=q.front();
res.push_ba

面试题32 – I. 从上到下打印二叉树最先出现在Python成神之路。