LeetCode: Convert Sorted Array to Binary Search Tree

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 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 *dfs(vector<int> &num, int beg, int len) {
13         if (!len) return NULL;
14         TreeNode *tmp = new TreeNode(num[beg+len/2]);
15         tmp->left = dfs(num, beg, len/2);
16         tmp->right = dfs(num, beg+len/2+1, (len-1)/2);
17         return tmp;
18     }
19     TreeNode *sortedArrayToBST(vector<int> &num) {
20         // Start typing your C/C++ solution below
21         // DO NOT write int main() function
22         int len = num.size();
23         if (!len) return NULL;
24         return dfs(num, 0, len);
25     }
26 };

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public int val;
 5  *     public TreeNode left;
 6  *     public TreeNode right;
 7  *     public TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public TreeNode SortedArrayToBST(int[] nums) {
12         int len = nums.Length;
13         if (len == 0) return null;
14         return dfs(nums, 0, len);
15     }
16     TreeNode dfs(int[] nums, int beg, int len)
17     {
18         if (len == 0) return null;
19         TreeNode tmp = new TreeNode(nums[beg + len / 2]);
20         tmp.left = dfs(nums, beg, len/2);
21         tmp.right = dfs(nums, beg+len/2+1, (len-1)/2);
22         return tmp;
23     }
24 }

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