题目：

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代码(首刷看解析 2024年1月11日）：

class MyLinkedList {
private:struct ListNode{int val;ListNode* next;ListNode(int val):val(val),next(nullptr){}};int size;ListNode* dummyHead;
public:MyLinkedList() {dummyHead = new ListNode(0);size = 0;}int get(int index) {if( index < 0 || index > size-1 ) return -1;ListNode* cur = dummyHead->next;while(index--){cur = cur->next;}return cur->val;}void addAtHead(int val) {ListNode* newNode = new ListNode(val);newNode->next = dummyHead->next;dummyHead->next = newNode;++size;}void addAtTail(int val) {ListNode* newNode = new ListNode(val);ListNode* cur = dummyHead;while(cur->next != nullptr){cur = cur->next;}cur->next = newNode;size++;}void addAtIndex(int index, int val) {if(index > size) return;if(index < 0) index = 0;ListNode* newNode = new ListNode(val);ListNode* cur = dummyHead;while(index--){cur = cur->next;}newNode->next = cur->next;cur->next = newNode;++size;}void deleteAtIndex(int index) {if(index >= size || index < 0) return;ListNode* cur = dummyHead;while(index--){cur=cur->next;}ListNode* tmp = cur->next;cur->next = cur->next->next;delete tmp;tmp=nullptr;--size;}
};/*** 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);*/

        写在文后：这道题太考验细节了，我因为各种小错误改了好久不对，最后实在没办法了和参考答案一行一行对才通过，发现是delete里的if中的第一个条件没有写=号，人晕了