struct DLinkListNode{
int val;
DLinkListNode *prev, *next;
DLinkListNode(int _val) : val(_val), prev(nullptr), next(nullptr){}
};
class MyLinkedList {
private:
int size;
DLinkListNode *head;
DLinkListNode *tail;
public:
MyLinkedList() {
this->size = 0;
this->head = new DLinkListNode(0);
this->tail = new DLinkListNode(0);
head->next = tail;
tail->prev = head;
}
int get(int index) {
if (index < 0 || index >= size){
return -1;
}
DLinkListNode *curr;
if(index + 1 < size - index){ //在链表左边
curr = head;
for(int i = 0; i <= index; ++i){
curr = curr->next;
}
}else{ //在链表右边
curr = tail;
for(int i = 0; i < size - index; i++){
curr = curr->prev;
}
}
return curr->val;
}
void addAtHead(int val) {
addAtIndex(0, val);
}
void addAtTail(int val) {
addAtIndex(size, val);
}
void addAtIndex(int index, int val) {
if(index > size){
return;
}
index = max(0, index);
DLinkListNode *pred, *succ;
if(index < size - index){ //插在左边
pred = head;
for(int i = 0; i <index; ++i){
pred = pred->next;
}
succ = pred->next;
}else{
succ = tail;
for(int i = 0; i < size - index; ++i){
succ = succ ->prev;
}
pred = succ -> prev;
}
size++;
DLinkListNode *toAdd = new DLinkListNode(val);
toAdd->prev = pred;
toAdd->next = succ;
pred->next = toAdd;
succ->prev =toAdd;
}
void deleteAtIndex(int index) {
if(index < 0 || index >= size){
return;
}
DLinkListNode *pred, *succ;
if(index < size - index){
pred = head;
for(int i = 0; i < index; ++i){
pred = pred->next;
}
succ = pred->next->next; //因为是带头节点的链表所以删除pred下一个才是index
}else{
succ = tail;
for(int i = 0; i < size - index - 1; ++i){
succ = succ->prev;
}
pred = succ->prev->prev; //同样带了尾节点删除元素为succ的上一个
}
size--;
DLinkListNode *p = pred->next;
pred->next = succ;
succ->prev =pred;
delete p;
}
};
/**
* Your MyLinkedList object will be instantiated and called as such:
* MyLinkedList* obj = new MyLinkedList();
* int param_1 = obj->get(index);
* obj->addAtHead(val);
* obj->addAtTail(val);
* obj->addAtIndex(index,val);
* obj->deleteAtIndex(index);
*/
class MyLinkedList {
int size;
ListNode head;
ListNode tail;
public MyLinkedList() {
size = 0;
head = new ListNode(0);
tail = new ListNode(0);
head.next = tail;
tail.prev = head;
}
public int get(int index) {
if (index < 0 || index >= size) {
return -1;
}
ListNode curr;
if (index + 1 < size - index) {
curr = head;
for (int i = 0; i <= index; i++) {
curr = curr.next;
}
} else {
curr = tail;
for (int i = 0; i < size - index; i++) {
curr = curr.prev;
}
}
return curr.val;
}
public void addAtHead(int val) {
addAtIndex(0, val);
}
public void addAtTail(int val) {
addAtIndex(size, val);
}
public void addAtIndex(int index, int val) {
if (index > size) {
return;
}
index = Math.max(0, index);
ListNode pred, succ;
if (index < size - index) {
pred = head;
for (int i = 0; i < index; i++) {
pred = pred.next;
}
succ = pred.next;
} else {
succ = tail;
for (int i = 0; i < size - index; i++) {
succ = succ.prev;
}
pred = succ.prev;
}
size++;
ListNode toAdd = new ListNode(val);
toAdd.prev = pred;
toAdd.next = succ;
pred.next = toAdd;
succ.prev = toAdd;
}
public void deleteAtIndex(int index) {
if (index < 0 || index >= size) {
return;
}
ListNode pred, succ;
if (index < size - index) {
pred = head;
for (int i = 0; i < index; i++) {
pred = pred.next;
}
succ = pred.next.next;
} else {
succ = tail;
for (int i = 0; i < size - index - 1; i++) {
succ = succ.prev;
}
pred = succ.prev.prev;
}
size--;
pred.next = succ;
succ.prev = pred;
}
}
class ListNode {
int val;
ListNode next;
ListNode prev;
public ListNode(int val) {
this.val = val;
}
}
class LsitNode:
def __init__(self, _val):
self.val = _val
self.prev = None
self.next = None
class MyLinkedList(object):
def __init__(self):
self.size = 0
self.head = LsitNode(0)
self.tail = LsitNode(0)
self.head.next = self.tail
self.tail.prev = self.head
def get(self, index):
if index < 0 or index >= self.size:
return -1;
if index + 1 < self.size - index:
curr = self.head
for __ in range(index + 1):
curr = curr.next
else:
curr = self.tail
for _ in range(self.size - index):
curr = curr.prev
return curr.val
def addAtHead(self, val):
"""
:type val: int
:rtype: None
"""
self.addAtIndex(0, val)
def addAtTail(self, val):
"""
:type val: int
:rtype: None
"""
self.addAtIndex(self.size, val)
def addAtIndex(self, index, val):
"""
:type index: int
:type val: int
:rtype: None
"""
if index > self.size:
return
index = max(0, index)
if index < self.size - index:
pred = self.head
for _ in range(index):
pred = pred.next
succ = pred.next
else:
succ = self.tail
for _ in range(self.size - index):
succ = succ.prev
pred = succ.prev
self.size += 1
to_add = ListNode(val)
to_add.prev = pred
to_add.next = succ
pred.next = to_add
succ.prev = to_add
def deleteAtIndex(self, index):
"""
:type index: int
:rtype: None
"""
if index < 0 or index >= self.size:
return
if index < self.size - index:
pred = self.head
for _ in range(index):
pred = pred.next
succ = pred.next.next
else:
succ = self.tail
for _ in range(self.size - index - 1):
succ = succ.prev
pred = succ.prev.prev
self.size -= 1
pred.next = succ
succ.prev = pred
# Your MyLinkedList object will be instantiated and called as such:
# obj = MyLinkedList()
# param_1 = obj.get(index)
# obj.addAtHead(val)
# obj.addAtTail(val)
# obj.addAtIndex(index,val)
# obj.deleteAtIndex(index)
浙公网安备 33010602011771号