LeetCode之Convert Sorted Array to Binary Search Tree

 /*采用分治法。排在中间的数作为根节点，前后段各作为左右子树，则左右
 子树的高度差不会大于1.因此，可以递归的构建左右子树，从而建立整个平衡
 二叉搜索树。*/
class Solution {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return sortedArrayToBST(nums, 0, nums.size()-1);
    }
    
    TreeNode* sortedArrayToBST(const vector<int> &nums, int left, int right){
        if(left > right) return nullptr;
        int mid = (left + right) / 2;
        TreeNode *root = new TreeNode(nums[mid]);
        root->left = sortedArrayToBST(nums, left, mid-1);
        root->right = sortedArrayToBST(nums, mid+1, right);
        return root;
    }
};