LeetCode 108. Convert Sorted Array to Binary Search Tree

二叉搜索树的建立是从两边来的。所以分左右递归来建立。代码如下：

class Solution { public: TreeNode* generateBST(int left, int right, vector<int>& num) { if (left > right) return nullptr; else if (left == right) return new TreeNode(num[left]); else { int mid = (left + right) / 2; TreeNode* node = new TreeNode(num[mid]); node->left = generateBST(left, mid - 1, num); node->right = generateBST(mid + 1, right, num); return node; } } TreeNode *sortedArrayToBST(vector<int> &num) { return generateBST(0, num.size() - 1, num); } };