struct TreeNode* bst_helper(struct ListNode **head, int size)
{
if(size == 0)
return NULL;
struct TreeNode *root = (struct TreeNode *)malloc(sizeof(struct TreeNode));
root->left = bst_helper(head,size/2);
root->val = (*head)->val;
(*head) = (*head)->next;
root->right = bst_helper(head,size - size/2 - 1);
return root;
}
struct TreeNode* sortedListToBST(struct ListNode* head) {
int size = get_size(head);
if(head == NULL)
return NULL;
return bst_helper(&head,size);
}
int is_bst2(bst *b)
{
if(!b || (!b->left && !b->right) )
return 1;
return bst_helper(b,INT_MIN,INT_MAX);
}
int bst_helper(bst *b, int min, int max)
{
if( !(min <= b->val && b->val < max))
return 0;
return bst_helper(b->left,min,b->val) && bst_helper(b->right,b->val+1,max);
}
