class Solution {

public:

```
TreeNode* sortedListToBST(ListNode* head) {
if (head == NULL) return NULL;
int len = 0;
ListNode *p = head;
while(p){
len++;
p = p->next;
}
return createTree(head, 0, len-1);
}
TreeNode *createTree(ListNode *node, int left, int right){
if (left > right) return NULL;
ListNode *p = node;
int mid = (left + right + 1)/2;
for (int i = left; i < mid; i++){
p = p->next;
}
TreeNode *root = new TreeNode(p->val);
root->left = createTree(node, left, mid-1);
root->right = createTree(p->next, mid+1, right);
return root;
}
```

};