Description

Submission

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
/**
 * 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 {
    TreeNode* dfs(ListNode* left, ListNode* right) {
        if(left == nullptr) return nullptr;
        if(left == right) return new TreeNode(left->val);
        // cout << left->val;
        
        if(left->next == right) {  
            TreeNode* r = nullptr;
            if(right) r = new TreeNode(right->val);
            return new TreeNode(left->val, nullptr, r);
        }

        ListNode *slow = left, *fast = left, *prevSlow = left;
        for(; fast != right && fast->next != right; prevSlow = slow, slow = slow->next, fast = fast->next->next);
        return new TreeNode(
            slow->val,
            dfs(left, prevSlow),
            dfs(slow->next, right)
        );
    }
public:
    TreeNode* sortedListToBST(ListNode* head) {
        if(head == nullptr) return nullptr;

        return dfs(head, nullptr);
    }
};