剑指offer 编程题（21）：二叉树层次打印

题目描述

从上往下打印出二叉树的每个节点，同层节点从左至右打印。

class Solution {public:    vector<int> PrintFromTopToBottom(TreeNode* root) {        queue<TreeNode*> q;        vector<int> res;        if(root == NULL)        {            return res;        }        q.push(root);        while(!q.empty())        {            res.push_back(q.front()->val);            if(q.front()->left!=NULL)                q.push(q.front()->left);            if(q.front()->right!=NULL)                q.push(q.front()->right);            q.pop();        }        return res;    }};

class Solution {public:    vector<int> PrintFromTopToBottom(TreeNode* root) {        vector<int> vec;        queue<TreeNode*> que;        if(root!=nullptr)            que.push(root);        while(!que.empty())        {            TreeNode* temp=que.front();            vec.push_back(temp->val);             que.pop();            if(temp->left){                que.push(temp->left);            };            if(temp->right) {                que.push(temp->right);            };        }        return vec;    }};