132 Construct-BST-from-sorted-array.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* solve(vector<int> &nums, int low, int high) {
        if(low>high)
            return NULL;
        
        int mid=(low+high)/2;
        
        TreeNode* root=new TreeNode;
        
        root->val=nums[mid];
        root->left=solve(nums,low,mid-1);
        root->right=solve(nums,mid+1,high);
        
        return root;
    }
    
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return solve(nums,0,nums.size()-1);
    }
};