Convert Sorted List to Binary Search Tree leetcode

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

方法一：把鏈表裏的元素放入數組，再進行查找

方法二：遍歷鏈表，設置快慢指針，找到中間元素，將該元素作爲根節點時間複雜度爲O(NlgN)

萬能的遞歸法，注意到有一點比較巧的是，由於單鏈表都是單向的。所以這裏我的查找區間設置爲左閉右開！這樣就避免了去找mid節點的前一個節點

class Solution {
public:
    TreeNode *sortedListToBST(ListNode *head) {
        return create(head,nullptr);
    }
    TreeNode* create(ListNode* head, ListNode* tail) {
        if(head == tail)
        return nullptr;
        ListNode* fast = head;
        ListNode* slow = head;
        while(fast != tail && fast->next != tail) {
            fast = fast->next->next;
            slow = slow->next;
        }
        TreeNode* root = new TreeNode(slow->val);//不能直接將listnode指針賦值給treenode
            root->left = create(head,slow);
            root->right = create(slow->next,tail);
        return root;
    }
};