designLinedList

designLinedList.cs

public class ListNode
{
    public int Val;
    public ListNode Next;
    public ListNode(int x = 0, ListNode Next = null)
    {
        Val = x;
        Next = Next;
    }
}

public class MyLinkedList {

    int length;
    ListNode dummyHead;
    public MyLinkedList() {
        length = 0;
        dummyHead = new ListNode();
    }
    
    public int Get(int index) {
        if (index < 0 || index >= length) return -1;

        var currentHead = dummyHead.Next;
        while (index > 0)
        {
            index--;
            currentHead = currentHead.Next;
        }
        return currentHead.Val;
    }
    
    public void AddAtHead(int val) {
        AddAtIndex(0, val);
    }
    
    public void AddAtTail(int val) {
        AddAtIndex(length, val);
    }
    
    public void AddAtIndex(int index, int val) {
        if (index < 0 || index > length) return;
        var currentHead = dummyHead;

        while (index > 0)
        {
            index--;
            currentHead = currentHead.Next;
        }
        var newNode = new ListNode(val, currentHead.Next);
        currentHead.Next = newNode;
        length++;
    }
    
    public void DeleteAtIndex(int index) {
        if (index < 0 || index >= length) return;
        var currentHead = dummyHead;
        while (index > 0)
        {
            index--;
            currentHead = currentHead.Next;
        }
        currentHead.Next = currentHead.Next.Next;
        length--;
    }
}