Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/
9 20
/
15 7
return its level order traversal as:
[ [3], [9,20], [15,7] ]
/**
* 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<vector<int>> levelOrder(TreeNode* root) {
queue<TreeNode*> nodes;
vector< vector<int> > result;
vector<int> tmp;
if(NULL==root)
return result;
nodes.push(root);
while(!nodes.empty())
{//读取的同时，把下一层压入队列当中
int length=nodes.size();
int i=0;
while(i<length)
{
TreeNode* tmpNode=nodes.front();
tmp.push_back(tmpNode->val);
if(tmpNode->left)
nodes.push(tmpNode->left);
if(tmpNode->right)
nodes.push(tmpNode->right);
nodes.pop();
i++;
}
result.push_back(tmp);
tmp.clear();
}
return result;
}
};