Java實作單鏈表

一、什么是單鏈表

單鏈表是鏈表的其中一種基本結構，在結點中資料域用來存盤資料元素，指標域用于指向下一個具有相同結構的結點，
因為只有一個指標結點，稱為單鏈表，

二、單鏈表的結構

三、單鏈表的基本操作

1.創建類和構造方法

class Node{
    public int val;
    public Node next;
    public Node(){

    }
    public Node(int val){
        this.val = val;
    }
}

2.建立單鏈表

public class MyLinkedList {
    public Node head;
    public void createLinkedList(){
        this.head = new Node(2);
        Node node2 = new Node(3);
        Node node3 = new Node(4);
        Node node4 = new Node(5);
        Node node5 = new Node(6);
        head.next = node2;
        node2.next = node3;
        node3.next = node4;
        node4.next = node5;
        node5.next = null;
    }
}

3.遍歷單鏈表

   public void traverse(){
        Node cur = head;
        while(cur != null){
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }

4.找到單鏈表的最后一個結點

   public Node findLastNode(){
        Node cur = head;
        if(cur == null){
            return null;
        }
        while(cur.next != null){
            cur = cur.next;
        }
        return cur;
    }

5.找到倒數第二個結點`

    public Node findLastTwoNode(){
        Node cur = head;
        if(cur == null){
            return null;
        }
        if(cur.next == null){
            return null;
        }
        while(cur.next.next != null){
            cur = cur.next;
        }
        return cur;
    }

6.求鏈表的長度

    public int size(){
        Node cur = head;
        int count = 0;
        while(cur != null){
            count++;
            cur = cur.next;
        }
        return count;
    }

7.求鏈表的第N個結點

    public Node findN(int n){
        if(head == null){
            System.out.println("單鏈表為空！");
            return null;
        }
        if(n <= 0){
            System.out.println("n不合法！");
        }
        if(n > size()){
            System.out.println("n不合法！");
        }
        int count = 1;
        Node cur = head;
        while(count != n){
            cur = cur.next;
            count++;
        }
        return cur;
    }

8.查找關鍵字key是否在單鏈表中

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

9.頭插

    public void addFirst(int data){
        Node node = new Node(data);
        node.next = head;
        head = node;
    }

10.尾插

    public void addLast(int data){
        Node node = new Node(data);
        Node cur = head;
        if(cur == null){
            head = node;
        }

        while(cur.next != null){
            cur = cur.next;
        }
        cur.next = node;
    }

11.任意位置的插入

    public void addIndex(int index,int data){
        if(index < 0 || index > size()){
            System.out.println("插入位置不合法！");
        }
        //頭插
        if(index == 0){
            addFirst(data);
            return;
        }
        //尾插
        if(index == size()){
            addLast(data);
            return;
        }
        //中間插
        Node node = new Node(data);
        Node cur = head;
        int count = 0;
        while(count != index-1){
            count++;
            cur = cur.next;
        }
        node.next = cur.next;
        cur.next = node;
    }

12.找到關鍵字為key的前一結點

    public  Node searchPre(int key){
        Node cur = head;
        while(cur.next != null){
            if(cur.next.val == key){
                return  cur;
            }
            cur = cur.next;
        }
        return null;
    }

13.洗掉關鍵字第一次為key的結點

    public void deleteKey(int key){
        if(head == null){
            return;
        }
        if(head.val == key){
            head = head.next;
            return;
        }
        Node prev = searchPre(key);
        if(prev == null){
            System.out.println("不存在關鍵字為key的結點");
        }else{
            prev.next = prev.next.next;
        }
    }

14.洗掉index位置的結點

   public void delete(int index){
        if(index < 0 || index >= size()){
            System.out.println("洗掉位置不合法！");
        }
        if(index == 0){
            head = head.next;
            return;
        }
        Node cur = head;
        int count = 0;
        while(count != index-1){
            cur = cur.next;
            count++;
        }
        cur.next = cur.next.next;
    }

15.清空單鏈表

    public void clear(){
        head = null;
    }