用于从链接列表中删除最后一次出现的项目的Java程序

使用指针，遍历整个列表并使用特殊指针跟踪包含最后出现键的节点之前的节点。在此之后，只需将下一个特殊指针的下一个存储到特殊指针的下一个中，以从链表中删除所需的节点。

Java

// Java program to implement
// the above approach
import java.io.*;
  
// A linked list Node
class Node
{
    int data;
    Node next;
     
    Node(int data)
    {
        this.data = data;
        this.next = null;
    }
}
 
class GFG{
 
// Function to delete the last
// occurrence
static Node deleteLast(Node head,
                       int x)
{
    Node temp = head;
    Node ptr = null;
     
    while (temp != null)
    {       
        // If found key, update
        if (temp.data == x)
            ptr = temp;
             
        temp = temp.next;
    }
   
    // If the last occurrence is the
    // last node
    if (ptr != null &&
        ptr.next == null)
    {
        temp = head;
         
        while (temp.next != ptr)
        {
            temp = temp.next;
        }
        temp.next = null;
    }
     
    // If it is not the last node
    if (ptr != null &&
        ptr.next != null)
    {
        ptr.data = ptr.next.data;
        temp = ptr.next;
        ptr.next = ptr.next.next;
    }
    return head;
}
 
// This function prints contents of
// linked list starting from the given
// Node
static void display(Node head)
{
    Node temp = head;
    if (head == null)
    {
        System.out.print("NULL");
        return;
    }
    while (temp != null)
    {
        System.out.print(temp.data +
                         " --> ");
        temp = temp.next;
    }
    System.out.print("NULL");
}
 
// Driver code
public static void main(String[] args)
{
    Node head = new Node(1);
    head.next = new Node(2);
    head.next.next = new Node(3);
    head.next.next.next =
    new Node(4);
    head.next.next.next.next =
    new Node(5);
    head.next.next.next.next.next =
    new Node(4);
    head.next.next.next.next.next.next =
    new Node(4);
     
    System.out.print(
           "Created Linked list: ");
    display(head);
     
    // Pass the address of the head
    // pointer
    head = deleteLast(head, 4);
    System.out.print(
           "List after deletion of 4: ");
    display(head);
}
}
// This code is contributed by patel2127

输出：

Created Linked list: 1 --> 2 --> 3 --> 4 --> 5 --> 4 --> 4 --> NULL
List after deletion of 4: 1 --> 2 --> 3 --> 4 --> 5 --> 4 --> NULL

给定一个链表和一个要删除的键。从链接中删除最后一次出现的键。该列表可能有重复项。

例子：

Input:   1->2->3->5->2->10, key = 2
Output:  1->2->3->5->10

这个想法是从头到尾遍历链表。遍历时，跟踪最后出现的键。遍历完整列表后，通过复制下一个节点的数据并删除下一个节点来删除最后一次出现。

Java

// A Java program to demonstrate deletion
// of last Node in singly linked list
class GFG{
     
// A linked list Node
static class Node
{
    int key;
    Node next;
};
 
static Node deleteLast(Node head,
                       int key)
{
    // Initialize previous of Node to
    // be deleted
    Node x = null;
 
    // Start from head and find the Node
    // to be deleted
    Node temp = head;
    while (temp != null)
    {
        // If we found the key,
        // update xv
        if (temp.key == key)
            x = temp;
 
        temp = temp.next;
    }
 
    // Key occurs at-least once
    if (x != null)
    {
        // Copy key of next Node to x
        x.key = x.next.key;
 
        // Store and unlink next
        temp = x.next;
        x.next = x.next.next;
 
        // Free memory for next
    }
    return head;
}
 
// Utility function to create a
// new node with given key
static Node newNode(int key)
{
    Node temp = new Node();
    temp.key = key;
    temp.next = null;
    return temp;
}
 
// This function prints contents of
// linked list starting from the given
// Node
static void printList( Node node)
{
    while (node != null)
    {
        System.out.printf(" %d ",
                          node.key);
        node = node.next;
    }
}
 
// Driver code
public static void main(String args[])
{
    // Start with the empty list
    Node head = newNode(1);
    head.next = newNode(2);
    head.next.next = newNode(3);
    head.next.next.next =
    newNode(5);
    head.next.next.next.next =
    newNode(2);
    head.next.next.next.next.next =
    newNode(10);
 
    System.out.printf("Created Linked List: ");
    printList(head);
    deleteLast(head, 2);
    System.out.printf(
           "Linked List after Deletion of 1: ");
    printList(head);
}
}
// This code is contributed by Arnab Kundu

输出：

Created Linked List: 
1  2  3  5  2  10 
Linked List after Deletion of 1: 
1  2  3  5  10

当要删除的节点是最后一个节点时，上述解决方案不起作用。
以下解决方案处理所有情况。

Java

// Java program to demonstrate deletion
// of last Node in singly linked list
class GFG{
 
// A linked list Node
static class Node
{
    int data;
    Node next;
};
 
// Function to delete the last
// occurrence
static void deleteLast(Node head,
                       int x)
{
    Node temp = head, ptr = null;
    while (temp!=null)
    {
        // If found key, update
        if (temp.data == x)
            ptr = temp;    
        temp = temp.next;
    }
 
    // If the last occurrence is the
    // last node
    if (ptr != null &&
        ptr.next == null)
    {
        temp = head;
        while (temp.next != ptr)
            temp = temp.next;
        temp.next = null;
    }
 
    // If it is not the last node
    if (ptr != null &&
        ptr.next != null)
    {
        ptr.data = ptr.next.data;
        temp = ptr.next;
        ptr.next = ptr.next.next;
        System.gc();
    }
}
 
/* Utility function to create a
   new node with given key */
static Node newNode(int x)
{
    Node node = new Node();
    node.data = x;
    node.next = null;
    return node;
}
 
// This function prints contents
// of linked list starting from
// the given Node
static void display(Node head)
{
    Node temp = head;
    if (head == null)
    {
        System.out.print("null");
        return;
    }
    while (temp != null)
    {
        System.out.printf("%d --> ",
                          temp.data);
        temp = temp.next;
    }
    System.out.print("null");
}
 
// Driver code
public static void main(String[] args)
{
    Node head = newNode(1);
    head.next = newNode(2);
    head.next.next = newNode(3);
    head.next.next.next =
    newNode(4);
    head.next.next.next.next =
    newNode(5);
    head.next.next.next.next.next =
    newNode(4);
    head.next.next.next.next.next.next =
    newNode(4);
    System.out.print(
    "Created Linked list: ");
    display(head);
    deleteLast(head, 4);
    System.out.print(
    "List after deletion of 4: ");
    display(head);
}
}
// This code is contributed by PrinciRaj1992

输出：

Created Linked List: 
1  2  3  4  5  4  4 
Linked List after Deletion of 1: 
1  2  3  4  5  4

有关详细信息，请参阅有关从链接列表中删除最后一个项目的完整文章！