//双向循环链表
class DbCirList extends DbList {
    constructor() {
        super();
        this.head.next = this.head;
        this.head.prev = this.head;
    }

    /**
     * 
     * @param item //插入的位置
     * @param element 插入的值
     */
    insert(item: any, element: any): void {
        if(this.find(item)) {
            return ;
        }
        if(this.find(element)) {
            return;
        }
        let currNode = this.find(item);
        let newNode = new NodeItem(element);
        newNode.next = currNode.next;
        newNode.prev = currNode;
        currNode.next&&(currNode.next.prev = newNode);
        currNode.next = newNode;
        this.size++;
    }

    /**
     * 
     * @param item 删除的值
     */
    remove(item: any): void {
        if (item === 'head') {
            this.head.next = this.head;
            this.head.prev = this.head;
            this.size = 0;
            return;
        }

        let currNode = this.find(item);

        if(currNode.next&&currNode.prev) {  // 如果存在值为item的节点
            currNode.next.prev = currNode.prev;
            currNode.prev.next = currNode.next;
            this.size--;
        }
    }

    /**
     * 
     * @param element 添加的值
     */
    append(element: any): void {
        let newNode = new NodeItem(element);
        let lastNode = this.findLast();
        newNode.next = lastNode.next;
        lastNode.next&&(lastNode.next.prev = newNode);
        lastNode.next = newNode;
        newNode.prev = lastNode;
        this.size++;
    }
}

let test = new DbCirList()

let arr = [1, 2, 3, 4, 5, 6, 7];

for(let i=0; i<arr.length; i++) {
    test.append(arr[i]);
}
test.remove(1);

test.display();