108.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return create(nums, 0, nums.size()-1); 
    }
    
    TreeNode* create(vector<int>& nums, int start, int end) {
        if (start == end) {
            return new TreeNode(nums[start]); 
        } else if (start > end) {
            return nullptr;
        }
        int mid = (start + end)/2;
        TreeNode *root = new TreeNode(nums[mid]);
        root->left = create(nums, start, mid-1);
        root->right = create(nums, mid+1, end);
        return root;
    }
};