LeetCode: Convert Sorted Array to Binary Search Tree

一次过

 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 };

 C#

 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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