将有序数组转换为二叉搜索树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
private:
    TreeNode* sortedArrayToBSTCore(const vector<int>& nums,int left,int right)
    {
        if(left>right)
            return nullptr;

        int mid=left+(right-left+1)/2;
        TreeNode* root=new TreeNode(nums[mid]);
        root->left=sortedArrayToBSTCore(nums,left,mid-1);
        root->right=sortedArrayToBSTCore(nums,mid+1,right);
        return root;
    }
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        if(nums.empty())
            return nullptr;
        
        return sortedArrayToBSTCore(nums,0,nums.size()-1); 
    }
};