TreeNode *sortedListToBST(ListNode *head) {
int len=0;
for(ListNode *p=head;p!=NULL;p=p->next) len++;
return sortedListToBST(head, 0, len-1);
}
TreeNode *sortedListToBST(ListNode *head) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
//return NULL;
if (head == NULL)
return NULL;
int len = 0;
ListNode * tmp = head;
while(tmp != NULL)
{
len++;
tmp = tmp->next;
}
tmp = head;
TreeNode * treehead = (TreeNode*) malloc(sizeof(TreeNode));
if (len == 1)
{
treehead->val = tmp->val;
treehead->left = NULL;
treehead->right = NULL;
return treehead;
}
if (len == 2)
{
TreeNode * treeright = new TreeNode(tmp->val);
treehead->val = tmp->next->val;
//treeright->val = tmp->val;
treehead->left = treeright;
treehead->right = NULL;
return treehead;
}
if (len == 3)
{
// bug here, should new
TreeNode * treeright = new TreeNode(tmp->val);
TreeNode * treeleft = new TreeNode(tmp->next->next->val);
treehead->val = tmp->next->val;
treehead->left = treeright;
treehead->right = treeleft;
return treehead;
}
int mid = len/2;
ListNode * lright = head;
ListNode * lleft = NULL;
TreeNode * tright = NULL;
TreeNode * tleft = NULL;
// // bug here, not malloc
TreeNode * thead = (TreeNode * ) malloc(sizeof(TreeNode));
int i=0;
tmp = head;
// bug here -1
while(i < mid-1)
{
tmp = tmp->next;
i++;
}
thead->val = tmp->next->val;
lleft = tmp->next->next;
tleft = sortedListToBST(lleft);
tmp->next = NULL;
tright = sortedListToBST(lright);
thead->left = tright;
thead->right = tleft;
return thead;
}
TreeNode* sortedListToBST(ListNode* head) {
if(head == NULL)
return NULL;
ListNode *r1 = head, *r2 = head;
TreeNode* root;
while(r2 != NULL && r2->next != NULL)
{
r1 = r1->next;
r2 = r2->next->next;
}
root = new TreeNode(r1->val);
root->val = r1->val;
ListNode* Left = NULL,*temp=NULL,*temp2 = head;
while(temp2 != r1)
{
if(temp == NULL)
{
temp = new ListNode(temp2->val);
temp->val = temp2->val;
Left = temp;
temp->next = NULL;
temp2 = temp2->next;
}
else
{
temp->next = new ListNode(temp2->val);
temp = temp->next;
temp->val = temp2->val;
temp->next = NULL;
temp2 = temp2->next;
}
}
root->left = sortedListToBST(Left);
ListNode* Right=NULL;
temp = NULL;
temp2 = r1->next;
while(temp2 != NULL)
{
if(temp == NULL)
{
temp = new ListNode(temp2->val);
temp->val = temp2->val;
Right = temp;
temp->next = NULL;
temp2 = temp2->next;
}
else
{
temp->next = new ListNode(temp2->val);
temp = temp->next;
temp->val = temp2->val;
temp->next = NULL;
temp2 = temp2->next;
}
}
root->right = sortedListToBST(Right);
return root;
}
struct TreeNode* sortedListToBST(struct ListNode* head) {
struct TreeNode* root;
struct ListNode *slow,*fast,*middle,*prev=NULL,*right;
slow=head;
fast=head;
if(head==NULL)
return NULL;
while(slow && fast)
{
if(fast->next == NULL)
{
middle = slow;
break;
}
if(fast->next->next == NULL)
{
middle=slow;
break;
}
prev = slow;
slow = slow->next;
fast = fast->next->next;
}
if(prev)
prev->next=NULL;
else
head=NULL;
right = middle->next;
root=(struct TreeNode*)malloc(sizeof(struct TreeNode));
root->val = middle->val;
printf("\n## %d",root->val);
root->left=sortedListToBST(head);
if(root->left)
printf(" ## %d",root->left->val);
root->right=sortedListToBST(right);
if(root->right)
printf("## %d\n",root->right->val);
return root;
}
void Main()
{
ListNode* list = createList({1, 2, 3, 4, 5});
print(sortedListToBST(list));
}
TreeNode *sortedListToBST(ListNode *head) {
curItem = head;
int listsize = getListSize(head);
return sortedListToBST(listsize);
}
