Java 一次迭代获取LinkedList的中间元素

在本文中，我们将了解如何在一次迭代中获取LinkedList的中间元素。java.util.LinkedList类的操作是可以进行预期的双向链表操作。索引到链表中的操作将从开始或结尾处遍历链表，取决于指定的索引离哪一个更近。

下面是一个演示示例−

假设我们的输入是： −

Input linked list: 100 200 330

所期望的输出将是 −

The middle element of the list is: 200

步骤

Step 1 - START
Step 2 - Declare a LinkedList namely input_list. Declare five node objects namely head, first_node, second_node, pointer_1, pointer_2.
Step 3 - Define the values.
Step 4 - Using a while loop, iterate over the linked list, get the middle element by traversing the list using pointer_1 and pointer_2 until pointer_1.next is not null.
Step 5 - Display the pointer_2 value as result.
Step 6 - Stop

示例1

在这里，我们将所有操作绑定在‘main’函数下。

public class LinkedList {
   Node head;
   static class Node {
      int value;
      Node next;
      Node(int d) {
         value = d;
         next = null;
      }
   }
   public static void main(String[] args) {
      LinkedList input_list = new LinkedList();
      input_list.head = new Node(100);
      Node second_node = new Node(200);
      Node third_node = new Node(330);
      input_list.head.next = second_node;
      second_node.next = third_node;
      Node current_node = input_list.head;
      System.out.print("The linked list is defined as: " );
      while (current_node != null) {
         System.out.print(current_node.value + " ");
         current_node = current_node.next;
      }
      Node pointer_1 = input_list.head;
      Node pointer_2 = input_list.head;
      while (pointer_1.next != null) {
         pointer_1 = pointer_1.next;
         if(pointer_1.next !=null) {
            pointer_1 = pointer_1.next;
            pointer_2 = pointer_2.next;
         }
      }
      System.out.println("\nThe middle element of the list is: " + pointer_2.value);
   }
}

输出

The linked list is defined as: 100 200 330
The middle element of the list is: 200

示例2

在这里，我们将操作封装到展示面向对象编程的函数中。

public class LinkedList {
   Node head;
   static class Node {
      int value;
      Node next;
      Node(int d) {
         value = d;
         next = null;
      }
   }
   static void get_middle_item(LinkedList input_list){
      Node pointer_1 = input_list.head;
      Node pointer_2 = input_list.head;
      while (pointer_1.next != null) {
         pointer_1 = pointer_1.next;
         if(pointer_1.next !=null) {
            pointer_1 = pointer_1.next;
            pointer_2 = pointer_2.next;
         }
      }
      System.out.println("\nThe middle element of the list is: " + pointer_2.value);
   }
   public static void main(String[] args) {
      LinkedList input_list = new LinkedList();
      input_list.head = new Node(100);
      Node second_node = new Node(200);
      Node third_node = new Node(330);
      input_list.head.next = second_node;
      second_node.next = third_node;
      Node current_node = input_list.head;
      System.out.print("The linked list is defined as: " );
      while (current_node != null) {
         System.out.print(current_node.value + " ");
         current_node = current_node.next;
      }
      get_middle_item(input_list);
   }
}

输出

The linked list is defined as: 100 200 330
The middle element of the list is: 200