在链表中制作菜单

Question

我想为这个链表添加一个用户菜单，但是程序没有运行。

程序允许用户在当前列表的末尾添加一个节点。
在当前列表的开头添加节点。 在特定索引处添加节点。 删除给定列表中的最后一个节点并更新尾节点。 删除给定列表中的第一个节点并更新头节点。 删除给定列表中给定索引处的节点并更新头节点。 检查列表中是否存在具有给定值的节点，返回 true 或 false。 检查列表中是否存在具有给定值的节点，返回给定值的索引 列表。

我运行它时什么也没有出现。 也没有错误信息。

你如何解决这个问题？

提前谢谢你。

class Node{
int val;
int target;
int index;
Node next;
Node head; 
Node tail;

public Node(int val){
    this.val = val;
                    }
{  
    int choice =0;  
    while(choice != 9)   
    {  
         System.out.println("\n\n*********Main Menu*********\n");  
         System.out.println("\nChoose one option from the following list ...\n");  
         System.out.println("\n1.Insert node\n2.Insert at start\n3.Insert certain index\n4.Remove node");
         System.out.println("\n5.Remove from the start\n6.Delete node after certain index\n7.Search for an element\n8.Search And Return Index\n9.Display nodes\n");     
         System.out.println("\nEnter your choice?\n");    

        switch(choice)  
        {  
            case 1:  
            addNode(val);      
            break;  
            case 2:  
            addNodeAtStart(val);         
            break;  
            case 3:  
            addNodeAtCertainIndex(val,index);       
            break;  
            case 4:  
            removeNode();       
            break;  
            case 5:  
            removeNodeAtStart();        
            break;  
            case 6:  
            removeNodeAtCertainIndex(index);          
            break;  
            case 7:  
            search(target);         
            break;  
            case 8:  
            searchAndReturnIndex(target);        
            break;  
            case 9:  
            printLinkedList();  
            break;  
            default:  
                System.out.println("Please enter valid choice..");  
        }  
    }  
}  


public void addNode(int val ){
    
    if(head==null){
    Node temp = new Node(val);
    head = temp;
    tail = temp;
    }else{
    tail.next = new Node(val);
    tail = tail.next;
    }
    }
public void addNodeAtStart(int val ){
    
    if(head==null){
    Node temp = new Node(val);
    head = temp;
    tail = temp;
    }else{
    Node temp = new Node(val);
    temp.next = head;
    head = temp;
    }
    }
public void addNodeAtCertainIndex(int val,int index){
      
     
    Node temp = head;
    int count = 0;
    while(temp!=null && ++count!=index)
    temp = temp.next;
    Node node = new Node(val);
    node.next = temp.next;
    temp.next = node;
    }
public void removeNode(){
    Node temp = head;
    while(temp.next!=null && temp.next.next!=null){
    temp = temp.next;
    }
    temp.next = null;
    tail = temp;
    }
public void removeNodeAtStart(){
    head = head.next;
    }
public void removeNodeAtCertainIndex(int index){
    
    Node temp = head;
    int count = 0;
    while(temp!=null && ++count!=index)
    temp = temp.next;
    temp.val = temp.next.val;
    temp.next = temp.next.next;
    }
public boolean search(int target){
     
    Node temp = head;
    while(temp!=null){
    if(temp.val == target)
    return true;
    }
    return false;
    }
public int searchAndReturnIndex(int target ){
    
    Node temp = head;
    int count = 0;
    while(temp!=null){
    count++;
    if(temp.val==target) return count;
    }
    return -1;
    }
public void printLinkedList(){
    System.out.println();
    Node temp = head;
    while(temp!=null){
    System.out.print(" "+temp.val);
    temp = temp.next;
    }
}

}

Answer 1

我做了一个更好的版本。

  import java.util.Scanner;

class Node{
int val;
int target;
int index;
Node next;
Node head; 
Node tail;

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

public void addNode(int val ){
    
    if(head==null){
    Node temp = new Node(val);
    head = temp;
    tail = temp;
    }else{
    tail.next = new Node(val);
    tail = tail.next;
    }
    }
public void addNodeAtStart(int val ){
    
    if(head==null){
    Node temp = new Node(val);
    head = temp;
    tail = temp;
    }else{
    Node temp = new Node(val);
    temp.next = head;
    head = temp;
    }
    }
public void addNodeAtCertainIndex(int val,int index){
      
     
    Node temp = head;
    int count = 0;
    while(temp!=null && ++count!=index)
    temp = temp.next;
    Node node = new Node(val);
    node.next = temp.next;
    temp.next = node;
    }
public void removeNode(){
    Node temp = head;
    while(temp.next!=null && temp.next.next!=null){
    temp = temp.next;
    }
    temp.next = null;
    tail = temp;
    }
public void removeNodeAtStart(){
    head = head.next;
    }
public void removeNodeAtCertainIndex(int index){
    
    Node temp = head;
    int count = 0;
    while(temp!=null && ++count!=index)
    temp = temp.next;
    temp.val = temp.next.val;
    temp.next = temp.next.next;
    }
public boolean search(int target){
     
    Node temp = head;
    while(temp!=null){
    if(temp.val == target)
    return true;
    }
    return false;
    }
public int searchAndReturnIndex(int target ){
    
    Node temp = head;
    int count = 0;
    while(temp!=null){
    count++;
    if(temp.val==target) return count;
    }
    return -1;
    }
public void printLinkedList(){
    System.out.println();
    Node temp = head;
    while(temp!=null){
    System.out.print(" "+temp.val);
    temp = temp.next;
    }
}

public class SinglyLinkedList
{    
    public void main(String[] args)
    {             
        Scanner scan = new Scanner(System.in);


        System.out.println("Singly Linked List\n");   
        
        char ch;
       
        do
        {
            System.out.println("\nChoose one option from the following list ...\n");  
            System.out.println("\n1.Insert node\n2.Insert at start\n3.Insert certain index\n4.Remove node");
            System.out.println("\n5.Remove from the start\n6.Delete node after certain index\n7.Search for an element\n8.Search And Return Index\n9.Display nodes\n");     
            System.out.println("\nEnter your choice?\n");  
            int choice;  
            choice = scan.nextInt();
                      
            switch (choice)
            {
            case 1 : 
                System.out.println("Enter integer element to insert");
                addNode( scan.nextInt() );  

                break;                          
            case 2 : 
                System.out.println("Enter integer element to insert");
                addNodeAtStart( scan.nextInt() );  

                break;                         
            case 3 : 
                System.out.println("Enter integer element to insert"); 
                addNodeAtCertainIndex(val,index);  
                break;                                          
            case 4 : 
                System.out.println("Enter integer element to remove"); 
                removeNode();
                break;
            case 5 : 
                System.out.println("Enter integer element to remove");
                removeNodeAtStart(); 
                break;                   
            case 6 : 
                System.out.println("Enter integer element to remove");
                removeNodeAtCertainIndex( scan.nextInt() );  

                break;  
            case 7 : 
                System.out.println("Enter integer element to search");
                search( scan.nextInt() );  

                break;   
            case 8 : 
                System.out.println("Enter integer element to search");
                searchAndReturnIndex( scan.nextInt() );  

                break;   
            case 9 :  
                printLinkedList();  
                break;      
                
             default : 
                System.out.println("Wrong Entry \n ");
                break;   
            }
           
            System.out.println("\nDo you want to continue (Type y or n) \n");
            ch = scan.next().charAt(0);                        
        } while (ch == 'Y'|| ch == 'y');               
    }

}

}

Answer 2

我通过重新安排东西修复了错误，但程序没有运行，但我希望这有助于给你一个想法。

class Node{
int val;
Node next;
Node head; 
Node tail;

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



public void addNode(){
    int val = 0;
    if(head==null){
    Node temp = new Node(val);
    head = temp;
    tail = temp;
    }else{
    tail.next = new Node(val);
    tail = tail.next;
    }
    }
public void addNodeAtStart(){
    int val = 0;
    if(head==null){
    Node temp = new Node(val);
    head = temp;
    tail = temp;
    }else{
    Node temp = new Node(val);
    temp.next = head;
    head = temp;
    }
    }
public void addNodeAtCertainIndex(){
    int val = 0; 
    int index = 0;
    Node temp = head;
    int count = 0;
    while(temp!=null && ++count!=index)
    temp = temp.next;
    Node node = new Node(val);
    node.next = temp.next;
    temp.next = node;
    }
public void removeNode(){
    Node temp = head;
    while(temp.next!=null && temp.next.next!=null){
    temp = temp.next;
    }
    temp.next = null;
    tail = temp;
    }
public void removeNodeAtStart(){
    head = head.next;
    }
public void removeNodeAtCertainIndex(){
    int index = 0;
    Node temp = head;
    int count = 0;
    while(temp!=null && ++count!=index)
    temp = temp.next;
    temp.val = temp.next.val;
    temp.next = temp.next.next;
    }
public boolean search(){
    int target = 0;
    Node temp = head;
    while(temp!=null){
    if(temp.val == target)
    return true;
    }
    return false;
    }
public int searchAndReturnIndex(){
    int target = 0;
    Node temp = head;
    int count = 0;
    while(temp!=null){
    count++;
    if(temp.val==target) return count;
    }
    return -1;
    }
public void printLinkedList(){
    System.out.println();
    Node temp = head;
    while(temp!=null){
    System.out.print(" "+temp.val);
    temp = temp.next;
    }
}


{  
    int choice =0;  
    while(choice != 9)   
    {  
         System.out.println("\n\n*********Main Menu*********\n");  
         System.out.println("\nChoose one option from the following list ...\n");  
         System.out.println("\n1.Insert node\n2.Insert at start\n3.Insert certain index\n4.Remove node");
         System.out.println("\n5.Remove from the start\n6.Delete node after certain index\n7.Search for an element\n8.Search And Return Index\n9.Display nodes\n");     
         System.out.println("\nEnter your choice?\n");    

        switch(choice)  
        {  
            case 1:  
            addNode();      
            break;  
            case 2:  
            addNodeAtStart();         
            break;  
            case 3:  
            addNodeAtCertainIndex();       
            break;  
            case 4:  
            removeNode();       
            break;  
            case 5:  
            removeNodeAtStart();        
            break;  
            case 6:  
            removeNodeAtCertainIndex();          
            break;  
            case 7:  
            search();         
            break;  
            case 8:  
            searchAndReturnIndex();        
            break;  
            case 9:  
            printLinkedList();  
            break;  
            default:  
                System.out.println("Please enter valid choice..");  
        }  
    }  
}  

}

Answer 3

您在 switch 语句中的方法调用需要一个参数。

// You call 
addNode();     
// required is
addNode(int val)
// which means you need to pass the value to be added in the switch 
//statement ;)
// Therefore the method calls without any parameter doesnt throw any error.
removeNode()