Java程序删除链表的备用节点

给定一个单链表，从第二个节点开始删除它的所有备用节点。例如，如果给定的链表是 1->2->3->4->5，那么你的函数应该将它转换为 1->3->5，如果给定的链表是 1->2-> 3->4 然后将其转换为 1->3。

方法1（迭代）：
跟踪要删除的节点的前一个。首先，改变前一个节点的下一个链接，迭代移动到下一个节点。

Java

// Java program to delete alternate 
// nodes of a linked list
class LinkedList
{
    // Head of list
    Node head;  
   
    // Linked list Node
    class Node
    {
        int data;
        Node next;
        Node(int d) 
        {
            data = d; 
            next = null; 
        }
    }
  
    void deleteAlt()
    {
       if (head == null) 
          return;
  
       Node prev = head;
       Node now = head.next;
  
       while (prev != null && 
              now != null) 
       {           
           // Change next link of previous node 
           prev.next = now.next;
  
           // Free node 
           now = null;
  
           // Update prev and now 
           prev = prev.next;
           if (prev != null) 
              now = prev.next;
       }
    }                 
  
                      
    // Utility functions 
    // Inserts a new Node at front 
    // of the list. 
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node new_node = new Node(new_data);
   
        // 3. Make next of new Node as head 
        new_node.next = head;
   
        // 4. Move the head to point to 
        // new Node 
        head = new_node;
    }
  
    // Function to print linked list 
    void printList()
    {
        Node temp = head;
        while(temp != null)
        {
           System.out.print(temp.data + " ");
           temp = temp.next;
        }  
        System.out.println();
    }
  
     // Driver code
    public static void main(String args[])
    {
        LinkedList llist = new LinkedList();
          
        /* Constructed Linked List is 
           1->2->3->4->5->null */
        llist.push(5);
        llist.push(4);
        llist.push(3);
        llist.push(2);
        llist.push(1);
          
        System.out.println(
               "Linked List before calling deleteAlt() ");
        llist.printList();
          
        llist.deleteAlt();
          
        System.out.println(
               "Linked List after calling deleteAlt() ");
        llist.printList();
    }
} 
// This code is contributed by Rajat Mishra

输出：

List before calling deleteAlt() 
1 2 3 4 5 
List after calling deleteAlt() 
1 3 5 

时间复杂度： O(n)，其中 n 是给定链表中的节点数。

方法2（递归）：
递归代码使用与方法 1 相同的方法。递归代码简单而简短，但会导致 O(n) 递归函数调用大小为 n 的链表。

Java

/* Deletes alternate nodes of 
   a list starting with head */
static Node deleteAlt(Node head) 
{ 
    if (head == null) 
        return; 
  
    Node node = head.next; 
  
    if (node == null) 
        return; 
  
    // Change the next link of head 
    head.next = node.next; 
  
  
    /* Recursively call for the new 
       next of head */
    head.next = deleteAlt(head.next); 
} 
// This code is contributed by Arnab Kundu

时间复杂度： O(n)

有关详细信息，请参阅有关删除链接列表的备用节点的完整文章！