Binary Tree Level Order Traversal II
Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ \
9 20
/ \
15 7
return its bottom-up level order traversal as:
[ [15,7] [9,20], [3], ]
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int> > out;
void levelTraval(vector<TreeNode* >& level)
{
if(level.size() > 0)
{
vector<TreeNode*> nextLevel;
for(int i = 0; i < level.size(); i++)
{
if(level[i]->left)
nextLevel.push_back(level[i]->left);
if(level[i]->right)
nextLevel.push_back(level[i]->right);
}
levelTraval(nextLevel);
vector<int> val;
for(int i = 0; i < level.size(); i++)
val.push_back(level[i]->val);
out.push_back(val);
}
}
vector<vector<int> > levelOrderBottom(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
out.clear();
vector<TreeNode*> v;
if(root != NULL)
{
v.push_back(root);
levelTraval(v);
}
return out;
}
};