(有头)链表的实现(Java)

一、初始化

java 复制代码

public class LinkedList {

    public class ListNode{
        int val = 0;
        ListNode next = null;
        public ListNode(int val){
            this.val = val;
            this.next = null;
        }
    }
    private ListNode head;
    private int size = 0;
    public LinkedList(){
        head = new ListNode(0);
        this.size = 0;
    }
}

二、头插

java 复制代码

    public void addFirst(int val){
        ListNode newNode = new ListNode(val);
        newNode.next = head.next;
        head.next = newNode;
        size++;
    }

三、尾插

java 复制代码

    public void addLast(int val){
        ListNode newNode = new ListNode(val);
        ListNode cur = head;
        while(cur.next != null){
            cur = cur.next;
        }
        cur.next = newNode;
        size++;
    }

四、指定位置插入（下标）

java 复制代码

    public void addIndex(int index, int val){
        if(index < 0 || index > size){
            return;
        }
        ListNode newNode = new ListNode(val);
        ListNode cur = head;
        while(index-- > 0){
            cur = cur.next;
        }
        newNode.next = cur.next;
        cur.next = newNode;
        size++;
    }

五、是否包含某个key

java 复制代码

    public boolean contains(int val){
        ListNode cur = head.next;
        while(cur != null){
            if(cur.val == val){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

六、删除某个节点

java 复制代码

    public void remove(int val){
        ListNode cur = head.next;
        ListNode prev = head;
        while(cur != null){
            if(cur.val == val){
                prev.next = cur.next;
                size--;
                break;
            }
            prev = cur;
            cur = cur.next;
        }
    }

七、删除所有的key

java 复制代码

    public void removeAllKeys(int val){
        ListNode cur = head;
        while(cur.next != null){
            if(cur.next.val == val){
                cur.next = cur.next.next;
            }else{
                cur = cur.next;
            }
        }
    }

八、size、打印、清理

java 复制代码

    public int size(){
        return size;
    }
    public void display(){
        ListNode cur = head.next;
        while(cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
    }
    public void clear(){
        head.next = null;
        size = 0;
    }