題目：

題解：

class Solution {
public:TreeNode* sortedArrayToBST(vector<int>& nums) {return helper(nums, 0, nums.size() - 1);}TreeNode* helper(vector<int>& nums, int left, int right) {if (left > right) {return nullptr;}// 選擇任意一個中間位置數字作為根節點int mid = (left + right + rand() % 2) / 2;TreeNode* root = new TreeNode(nums[mid]);root->left = helper(nums, left, mid - 1);root->right = helper(nums, mid + 1, right);return root;}
};