c#-单链表

namespace MyLink;
public class MyLinkedList {
    private int _size{get;set;}
    public class MyTreeNode{
        public int val{get;set;}
        public MyTreeNode next{get;set;}

        public MyTreeNode(int val)
        {
            this.val = val;
        }
    }
    public MyTreeNode head{get;set;}
    public MyLinkedList() {
        head = new MyTreeNode(0); //虚拟头结点
        this._size = 0;
    }
    
    public int Get(int index) {
        if(index < 0 || index >= this._size) return -1;
        var cur = head.next;
        while(index != 0) // 举个案例来测试边界 如 index=0，这个循环就不会执行
        {
            cur = cur.next;
            index--;
        }
        return cur.val;
    }
    
    public void AddAtHead(int val) {
        var newHead = new MyTreeNode(val);
        newHead.next = head.next;
        head.next = newHead;
        this._size ++;
    }
    
    public void AddAtTail(int val) {
        var cur = head; // 指向虚拟节点 *
        while(cur.next != null)
        {
            cur = cur.next;
        } 
        cur.next = new MyTreeNode(val);
        this._size++;
    }
    
    public void AddAtIndex(int index, int val) {
        var newNode = new MyTreeNode(val);
        var cur = head;
        while(index != 0)
        {
            cur = cur.next;
            if(cur == null) break;
            index --;
        }
        if(cur != null)
        {
            newNode.next = cur.next;
            cur.next = newNode;
            this._size++;
        }            
    }
    
    public void DeleteAtIndex(int index) {
        if(index < this._size){
            var cur = head;
            while(index != 0)
            {
                cur = cur.next;
                if(cur == null) return;
                index--;
            }
            if (cur != null)
            {
                cur.next = cur.next.next;
                this._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);
 */

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