Convert Sorted List to Binary Search Tree

Convert Sorted List to Binary Search Tree

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

TreeNode *sortedListToBST(ListNode *head) {
return sortedListToBST(head,listLength(head));
}

TreeNode* sortedListToBST(ListNode* head,int len)
{
if(len ==0) return nullptr;
if(len ==1) return new TreeNode(head->val);
TreeNode* root =new TreeNode(nth_node(head,len/2+1)->val);
root->left =sortedListToBST(head,len/2);
root->right =sortedListToBST(nth_node(head,len/2+2),(len-1)/2);
return root;
}

int listLength(ListNode* node)
{
int n=0;
while(node)
{
++n;
node =node->next;
}
return n;
}

ListNode* nth_node(ListNode* node,int n)
{
while(--n)
{
node =node->next;
}
return node;
}