单链表相关

单链表创建总结

*创建 ListNode 结点类 有属性 val next 考虑现实使用val定义为一个no和若干val，toString()重写

*创建 SingleLinkedList 单链表类 有private属性 头指针head 需要初始化

*单链表类需要有的方法：

*遍历方法：不为空、则从头指针.next首元结点开始遍历，直至尾部

*插入结点：分头插法、尾插法（temp指针向后移动直至尾部、temp.next = 入参）

*修改结点：不为空、则从头指针.next首元结点开始遍历，直至no相等/找不到no，修改val

*删除结点：从头指针.next首元结点开始遍历，直至no相等/找不到no，temp指向next.next

package LeetcodeExercise;

import java.awt.*;

public class SingleLinkedListTest {
    public static void main(String[] args) {
        ListNode n1 = new ListNode(1,"111");
        ListNode n2 = new ListNode(2,"222");
        ListNode n3 = new ListNode(3,"333");

        SingleLinkedList singleLinkedList = new SingleLinkedList();
        singleLinkedList.insertNodeTail(n1);
        singleLinkedList.insertNodeTail(n2);
        singleLinkedList.insertNodeTail(n3);

        singleLinkedList.list();
        singleLinkedList.updateNode(new ListNode(2,"789"));
        singleLinkedList.deleteNode(1);
        singleLinkedList.list();

    }
}

class ListNode{

    int no;
    String value;
    ListNode next;
    public ListNode(int no, String value) {
        this.no = no;
        this.value = value;
        this.next = null;
    }

    public int getNo() {
        return no;
    }

    public void setNo(int no) {
        this.no = no;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public ListNode getNext() {
        return next;
    }

    public void setNext(ListNode next) {
        this.next = next;
    }

    @Override
    public String toString() {
        return "ListNode{" +
                "no=" + no +
                ", value=" + value +
                '}';
    }
}

class SingleLinkedList{
    private ListNode head = new ListNode(0," ");//head不能动

    //遍历
    public void list(){
        if(isEmpty()){
            return;
        }
        ListNode temp = head.next;
        while (true){
            if(temp == null){
                break;
            }
            System.out.println(temp);
            temp = temp.next;
        }

    }

    public boolean isEmpty(){
        if(head.next == null){
            System.out.println("空链表");
            return true;
        }
        return false;
    }

    //根据no找到结点 ???考虑怎么复用 到底返回what
    public ListNode listByNo(int no){
        if(isEmpty()){
            return null;
        }
        ListNode temp = head.next;
        while (temp.no != no){
            temp = temp.next;
        }
        System.out.println(temp);
        return temp;
    }

    /**
     * @description: 尾部插入节点
     * @params [val] 值
     * @return LeetcodeExercise.ListNode
     */
    public void insertNodeTail(ListNode listNode){
        ListNode temp = head;
        while (true){
            if(temp.next == null){
                break;
            }
            temp = temp.next;
        }
        temp.next = listNode;

    }

    public void updateNode(ListNode listNode){
        if(isEmpty()){
            return;
        }
        ListNode temp = head.next;
        boolean flag = false;
        while (true){
            if(temp == null) {
                break;
            }
            if(temp.no == listNode.no){
                flag = true;
                break;
            }
            temp = temp.next;
        }
        if(flag){
            temp.value = listNode.value;
        }else {
            System.out.println("no listnode.no like this!");
        }
    }

    public void deleteNode(int no){
        ListNode temp = head;
        boolean flag = false;
        while (true){
            if(temp == null) {
                break;
            }
            if(temp.no == no){
                flag = true;
                break;
            }
            temp = temp.next;
        }

        if(flag){
            temp.next = temp.next.next;
        }else {
            System.out.println("no listnode.no like this!");
        }


    }


}