Lintcode(M) 二叉树的层次遍历

二叉树的层次遍历

描述

笔记

数据

评测

给出一棵二叉树，返回其节点值的层次遍历（逐层从左往右访问）

您在真实的面试中是否遇到过这个题？ Yes

样例

给一棵二叉树 {3,9,20,#,#,15,7} ：

3

/ \

9 20

/ \

15 7

返回他的分层遍历结果：

[

[3],

[9,20],

[15,7]

]

/**
* Definition of TreeNode:
* class TreeNode {
* public:
*     int val;
*     TreeNode *left, *right;
*     TreeNode(int val) {
*         this->val = val;
*         this->left = this->right = NULL;
*     }
* }
*/

class Solution {
/**
* @param root: The root of binary tree.
* @return: Level order a list of lists of integer
*/
public:
vector<vector<int>> levelOrder(TreeNode *root) {
// write your code here
vector<vector<int>> v;
if(root==NULL) return v;
queue<TreeNode*> q;
q.push(root);

while(!q.empty()){vector<int> level; int  size=q.size();
for(int i=0;i<size;++i){

TreeNode* node=q.front();
q.pop();

level.push_back(node->val);
if(node->left)
q.push(node->left);
if(node->right)
q.push(node->right);
}
v.push_back(level);
}
return v;
}
};

犯过错误点：while 和for的顺序

是while(!q.empty()) 而不是while(!q)