Java数据结构之单链表的实现与面试题汇总

public class Studentnode {
    public String no; //学号
    public String name; //姓名
    public int age; //年龄
    public StudentNode next; //指向下一个节点

    //构造器
    public StudentNode(String no, String name, int age ){
        this.no = no;
        this.name = name;
        this.age = age;
    }

    //为了显示方便
    @Override
    public String toString() {
        return "StudentNode{" +
                "no='" + no + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

public class StudentLinkedList {
    //初始化头节点
    private StudentNode head = new StudentNode("", "", 0);

	  //获取头节点
    public StudentNode getHead() {
        return head;
    }

    //添加节点
    //1.找到当前链表的最后节点
    //2.将最后节点的next指向新的节点
    public void add(StudentNode studentNode) {
        StudentNode temp = head;
        //遍历链表找到最后的节点
        while (temp.next != null) {
            //没有找到，就后移
            temp = temp.next;
        }
        //最后的节点的next指向新节点
        temp.next = studentNode;
    }

    //遍历 显示链表
    public void showList(){
        //判断链表是否为空
        if (head.next == null){
            System.out.println("当前链表为空");
            return;
        }
        //遍历 使用辅助指针
        StudentNode temp = head;
        while (temp != null){
            //更新指针
            temp = temp.next;
            if (temp.next == null){
                System.out.print(temp);
                break;
            }
            System.out.print(temp + "--->");
        }
    }

    //插入节点
    //根据学号顺序查找添加的位置, 如果存在, 则提示错误信息
    public void addByOrder(StudentNode studentNode){
        //寻找的temp应该为添加位置的前一个节点
        StudentNode temp = head;
        boolean flag = false; //标识新添加的no是否已经存在
        while (true){
            if (temp.next == null){
                //已经在链表的尾部
                break;
            }
            if (Integer.parseInt(temp.next.no) > Integer.parseInt(studentNode.no)){
                //位置找到 插入到temp后
                break;
            }else if (Integer.parseInt(temp.next.no) == Integer.parseInt(studentNode.no)){
                //已经存在
                flag = true;
                break;
            }
            //移动指针
            temp = temp.next;
        }
        if (flag){
            System.out.println("\n准备插入的学生信息: " + studentNode.no + "，该学号已经存在，不可添加！");
        }else {
            studentNode.next = temp.next;
            temp.next = studentNode;
        }
    }

    //根据no学号修改学生信息
    public void update(StudentNode studentNode){
        if (head.next == null){
            System.out.println("当前链表为空, 无法修改");
            return;
        }
        StudentNode temp = head.next;
        boolean flag = false; //表示是否找到节点
        while (true){
            if (temp == null){
                break;
            }
            if (temp.no == studentNode.no){
                flag = true;
                break;
            }
            temp = temp.next;
        }
        if (flag){
            temp.name = studentNode.name;
            temp.age = studentNode.age;
        }else {
            System.out.println("没有找到");
        }
    }

    //删除节点
    public void delete(String no){
        StudentNode temp = head;
        boolean flag = false; //标志是否找到
        //查找到待删除节点的前一个节点进行删除操作
        while (true){
            if (temp.next == null){
                //到达尾部
                break;
            }
            if (temp.next.no == no){
                //找到了
                flag = true;
                break;
            }
            //遍历
            temp = temp.next;
        }
        //删除操作
        if (flag){
            temp.next = temp.next.next;
            System.out.println("删除成功！");
        }else {
            System.out.println("要删除的节点不存在！");
        }
    }
}

public class StudentListTest {

    public static void main(String[] args) {
        StudentNode node1 = new StudentNode("1", "黄小黄", 21);
        StudentNode node2 = new StudentNode("2", "懒羊羊", 21);
        StudentNode node3 = new StudentNode("3", "沸羊羊", 22);
        //创建单链表 录入数据 输出
        StudentLinkedList list = new StudentLinkedList();
        list.add(node1);
        list.add(node2);
        list.add(node3);
        System.out.println("遍历链表:");
        list.showList();
        //测试插入数据方法
        StudentNode node5 = new StudentNode("5", "美羊羊", 19);
        StudentNode node4 = new StudentNode("4", "暖羊羊", 19);
        list.addByOrder(node5);
        list.addByOrder(node4);
        System.out.println("\n依次插入学号为5、4的学生后:");
        list.showList();
        //测试修改方法
        System.out.println("\n测试修改方法:");
        list.update(new StudentNode("1", "祢豆子", 10));
        list.showList();
        //测试删除方法
        System.out.println("\n测试删除方法:");
        list.delete("1");
        list.delete("5");
        list.showList();
    }
}

 
    public static int getLength(StudentNode head){
        if (head.next == null){
            return 0;
        }
        int length = 0;
        StudentNode temp = head.next;
        while (temp != null){
            length++;
            temp = temp.next;
        }
        return length;
    }

    public static StudentNode findLastIndexNode(StudentNode head, int index){
        //如果链表为空
        if (head.next == null){
            return null;
        }
        //得到链表的长度(节点个数)
        int size = getLength(head);
        //遍历 size-index次 得到倒数第index个节点
        //数据校验
        if (index <= 0 || index > size){
            return null;
        }
        //遍历
        StudentNode current = head.next;
        for (int i = 0; i < size - index; i++) {
            current = current.next;
        }
        return current;
    }

	
    public static StudentLinkedList reverseList(StudentNode head){
        if (head.next == null){
            return null;
        }
        StudentNode old = head.next; //用于遍历旧链表
        //创建新链表，新链表根据原链表遍历得到
        StudentLinkedList newList = new StudentLinkedList();
        StudentNode newHead = newList.getHead(); //新链表的头节点
        //遍历构造
        boolean flag = true; //标记是否为第一次添加
        while (old != null){
            //头插法加入到新链表中
            StudentNode newNode = new StudentNode(old.no, old.name, old.age);
            if(flag){
                newHead.next = newNode;
                newNode.next = null;
                flag = false;
            }else {
                newNode.next = newHead.next;
                newHead.next = newNode;
            }
            old = old.next;
        }
        return newList;
    }

	
    public static void reverse(StudentNode head){
        //如果当前链表为空 或者只有一个节点 直接返回即可
        if (head.next == null || head.next.next == null){
            return;
        }
        //辅助指针遍历原来的链表
        StudentNode cur = head.next; //当前节点
        StudentNode next = null; //指向cur的下一个节点
        StudentNode reverseHead = new StudentNode("", "", 0);
        //遍历原来的链表，每遍历一个节点，就取出，放在新链表的最前端
        while (cur != null){
            next = cur.next; //暂时保存当前节点的下一个节点
            cur.next = reverseHead.next; //讲cur下一个节点放在链表最前端
            reverseHead.next = cur;
            cur = next; //cur后移动
        }
        head.next = reverseHead.next;
        return;
    }

    
    public static void reversePrintList(StudentNode head){
        if (head.next == null){
            return; //空链表无法打印
        }
        //创建栈模拟逆序打印
        Stack<StudentNode> stack = new Stack<>(); //栈
        StudentNode cur = head.next;
        //将链表的所有节点压入栈
        while (cur != null){
            stack.push(cur);
            cur = cur.next;
        }
        //逆序打印
        while (!stack.empty()){
            //出栈
            System.out.println(stack.pop());
        }
        return;
    }