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。

 

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