int height(TreeNode* node){

if(!node) return 0;

return max(height(node->left),height(node->right))+1;

}

void traverseLevel(TreeNode* node,int level,vector<int> &temp){

if(!node) return;

if(level==1) temp.push_back(node->val);

traverseLevel(node->left,level-1,temp);

traverseLevel(node->right,level-1,temp);

}

vector<vector<int>> levelOrderBottom(TreeNode* root) {

vector<vector<int>> v;

vector<int> temp;

int h=height(root);

for(int level=h;level>0;level--){

traverseLevel(root,level,temp);

v.push_back(temp);

temp.clear();

}

return v;

}