ListNode* insertionSortList(ListNode* head) {
if (!head || !head->next) return head;
ListNode fakeHead(INT_MIN);
fakeHead.next = head;
auto curr = head->next;
head->next = nullptr;
while(curr) {
auto prev = &fakeHead, next = curr->next, sorted = fakeHead.next;
while (prev) {
if (!sorted) {
prev->next = curr;
curr->next = nullptr;
break;
}
if (prev->val <= curr->val && curr->val < sorted->val) {
prev->next = curr;
curr->next = sorted;
break;
} else {
prev = sorted;
sorted = sorted->next;
}
}
curr = next;
}
return fakeHead.next;
}
ListNode *partition(ListNode *head, int x) {
ListNode fakeHead(0);
fakeHead.next = head;
head = &fakeHead;
ListNode *pos = NULL;
for(ListNode *p = head; p!=NULL && p->next!=NULL; ){
if (!pos && p->next->val >= x){
pos = p;
p=p->next;
continue;
}
if (pos && p->next->val < x){
ListNode *pNext = p->next;
p->next = pNext->next;
pNext->next = pos->next;
pos->next = pNext;
pos = pNext;
continue;
}
p=p->next;
}
return head->next;
}
ListNode *removeNthFromEnd(ListNode *head, int n) {
if (head==NULL || n<=0){
return NULL;
}
ListNode fakeHead(0);
fakeHead.next=head;
head=&fakeHead;
ListNode *p1, *p2;
p1=p2=head;
for(int i=0; i<n; i++){
if (p2==NULL) return NULL;
p2=p2->next;
}
while (p2->next!=NULL){
p2=p2->next;
p1=p1->next;
}
p1->next = p1->next->next;
return head->next;
}
ListNode* deleteDuplicates(ListNode* head) {
ListNode fakeHead(-1);
fakeHead.next = head;
ListNode *pre = &fakeHead;
while(head) {
ListNode *next = head->next;
if (next == NULL || next->val != head->val) {
pre = head;
head = head->next;
continue;
}
while (next != NULL && next->val == head->val) {
head->next = next->next;
delete next;
next = head->next;
}
pre->next = head->next;
delete head;
head = pre->next;
}
return fakeHead.next;
}
