Description
https://oj.leetcode.com/problems/binary-tree-level-order-traversal-ii/
Difficulty: 0.5/5.0 star
Related: https://oj.leetcode.com/problems/binary-tree-level-order-traversal/
Analysis and solution
It is almost the same with the old problem. All you have to do is to reverse the result vector.
class Solution {
public:
vector<vector<int> > levelOrderBottom(TreeNode *root) {
vector<vector<int> > result;
traverse(root, 0, result);
reverse(result.begin(), result.end());
return result;
}
void traverse(TreeNode * pt, int level, vector<vector<int> > & result){
if (pt == NULL)
return;
if (result.size() == level)
result.push_back(vector<int>());
result[level].push_back(pt->val);
traverse(pt->left, level + 1, result);
traverse(pt->right, level + 1, result);
}
};