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 *sortedArrayToBST(vector<int> &num) {
13         // Start typing your C/C++ solution below
14         // DO NOT write int main() function
15         TreeNode *t;
16         int len=num.size();
17         int mid=len/2;
18         if(num.size()==0)
19             return NULL;
20         if(num.size()==1)
21         {
22             t=(TreeNode *)malloc(sizeof(struct TreeNode));
23             t->val=num[0];
24             t->left=t->right=NULL;
25             return t;
26         }
27         t=(TreeNode *)malloc(sizeof(struct TreeNode));
28         t->val=num[mid];
29         vector<int>v1(num.begin(),num.begin()+mid);
30         vector<int>v2(num.begin()+mid+1,num.end());
31         t->left=sortedArrayToBST(v1);
32         t->right=sortedArrayToBST(v2);
33         return t;
34     }
35 };