Find First Bad Version

来源：Lintcode

原帖：http://www.lintcode.com/en/problem/first-bad-version/

题目：
The code base version is an integer and start from 0 to n. One day, someone commit a bad version in the code case,  so it caused itself and the following versions are all failed in the unit tests. You can determine whether a version is bad by the following interface: boolean isBadVersion(int version);
Find the first bad version.

代码：

 struct TreeNode {  
   int val;  
   TreeNode* left;  
   TreeNode* right;  
   TreeNode(int v) : val(v), left(NULL), right(NULL) {}  
 };  
   
   
 void find_k_largest_in_BST_helper(TreeNode* root, int k, vector<int> &k_elements) {  
   if (!root || k_element.size() == k) {  
     return;  
   }  
   // Perform reverse inorder traversal  
   if (root && k_elements.size() < k) {  
     find_k_largest_in_BST_helper(root->right, k, k_elements);  
     if (k_elements.size() < k) {  
       k_elements.push_back(root->val);  
       find_k_largest_in_BST_helper(root->left, k, k_elements);  
     }  
   }  
 }  
   
 vector<int> find_k_largest_in_BST(TreeNode* root, int k) {  
   vector<int> k_elements;  
   find_k_largest_in_BST_helper(root, k , k_elements);  
   return k_elements;  
 }