lintcode-二叉树的层次遍历 II

描述

样例

3
/ \
9  20
/  \
15   7

[
[15,7],
[9,20],
[3]
]

代码

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

#include<queue>
#include<algorithm>
class Solution {
public:
/*
* @param root: A tree
* @return: buttom-up level order a list of lists of integer
*/
vector<vector<int>> levelOrderBottom(TreeNode * root) {
// write your code here
TreeNode * q=root;
vector<vector<int>> res;
if(root==NULL){
return res;
}
queue<TreeNode *> childs;
childs.push(q);
TreeNode * tt=NULL;
int len=1;
while(!childs.empty()){
vector<int> temp;
len=childs.size();
while(len--){
temp.push_back(childs.front()->val);
tt=childs.front();
childs.pop();
if(tt->left!=NULL){
childs.push(tt->left);
}
if(tt->right!=NULL){
childs.push(tt->right);
}
}
res.push_back(temp);

}
reverse(res.begin(),res.end());
return res;
}
};