LeetCode – Refresh – Convert Sorted Array to Binary Search Tree

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     TreeNode *getTree(const vector<int> &num, int start, int end) {
13         if (start > end) return NULL;
14         int mid = (start + end)/2;
15         TreeNode *root = new TreeNode(num[mid]);
16         root->left = getTree(num, start, mid-1);
17         root->right = getTree(num, mid+1, end);
18         return root;
19     }
20     TreeNode *sortedArrayToBST(vector<int> &num) {
21         return getTree(num, 0, num.size()-1);
22     }
23 };