LeetCode: Convert Sorted Array to Binary Search Tree

一次过

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode *dfs(vector<int> &num, int beg, int len) {
        if (!len) return NULL;
        TreeNode *tmp = new TreeNode(num[beg+len/2]);
        tmp->left = dfs(num, beg, len/2);
        tmp->right = dfs(num, beg+len/2+1, (len-1)/2);
        return tmp;
    }
    TreeNode *sortedArrayToBST(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int len = num.size();
        if (!len) return NULL;
        return dfs(num, 0, len);
    }
};

 C#

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode SortedArrayToBST(int[] nums) {
        int len = nums.Length;
        if (len == 0) return null;
        return dfs(nums, 0, len);
    }
    TreeNode dfs(int[] nums, int beg, int len)
    {
        if (len == 0) return null;
        TreeNode tmp = new TreeNode(nums[beg + len / 2]);
        tmp.left = dfs(nums, beg, len/2);
        tmp.right = dfs(nums, beg+len/2+1, (len-1)/2);
        return tmp;
    }
}