从单向链表中删除所有偶数节点的程序

给定一个包含N 个节点的单向链表，任务是从列表中删除所有偶数节点。

例子：

Input: LL = 1 -> 4 -> 3 -> 18 -> 19 
Output: 1 -> 3 -> 19
Input: LL = 5 -> 3 -> 6 -> 8 -> 4 -> 1 -> 2 -> 9 
Output: 5 -> 3 -> 1 -> 9 
 

方法：

• 思路是将单向链表的节点一一遍历，得到偶数数据节点的指针。按照本文中使用的方法删除这些节点。

下面是上述想法的实现：

C++

// C++ implementation to delete all
// even nodes from the singly linked list
 
#include 
using namespace std;
 
// Node of the singly linked list
struct Node
{
    int data;
    struct Node* next;
};
 
// Function to insert a node at
// the beginning of the singly
// Linked List
void push(struct Node** head_ref,
          int new_data)
{
    struct Node* new_node
        = (struct Node*)malloc(
            sizeof(
                struct Node));
 
    new_node->data = new_data;
    new_node->next = (*head_ref);
    (*head_ref) = new_node;
}
 
// Function to delete a node in a
// singly Linked List.
// head_ref --> Pointer to head
// node pointer.
// key --> Node to be deleted
void deleteNode(struct Node** head_ref,
                int key)
{
    // Store head node
    struct Node *temp = *head_ref,
                *prev;
 
    // If head node itself holds
    // the key to be deleted
    if (temp != NULL
        && temp->data == key) {
        // Changed head
        *head_ref = temp->next;
        // Free old head
        free(temp);
        return;
    }
 
    // Search for the key to be
    // deleted, keep track of the
    // previous node as we need
    // to change 'prev->next'
    while (temp != NULL
           && temp->data != key) {
        prev = temp;
        temp = temp->next;
    }
 
    // If key was not present
    // in linked list
    if (temp == NULL)
        return;
 
    // Unlink the node from
    // linked list
    prev->next = temp->next;
 
    // Free memory
    free(temp);
}
 
// Function to delete all the
// even nodes from the
// singly linked list
void deleteEvenNodes(Node** head_ref)
{
    Node* ptr = *head_ref;
    // Node* next;
 
    while (ptr != NULL) {
        // next = ptr->next;
        // If true, delete node 'ptr'
        if (ptr->data % 2 == 0)
            deleteNode(head_ref,
                       ptr->data);
        ptr = ptr->next;
    }
}
 
// This function prints contents
// of linked list starting from
// the given node
void printList(struct Node* node)
{
    while (node != NULL) {
        printf(" %d -> ", node->data);
        node = node->next;
    }
}
 
// Driver code
int main()
{
    // Start with the empty list
    Node* head = NULL;
    push(&head, 19);
    push(&head, 18);
    push(&head, 3);
    push(&head, 4);
    push(&head, 1);
 
    printf("Initial List: ");
    printList(head);
 
    deleteEvenNodes(&head);
 
    printf("\nFinal List: ");
    printList(head);
}

Java

// Java implementation to delete all
// even nodes from the singly 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;
    }
}
 
// Function to insert a node at
// the beginning of the singly
// Linked List
public void push(int new_data)
{
    Node new_node = new Node(new_data);
    new_node.next = head;
    head = new_node;
}
 
// Function to delete a node in a
// singly Linked List.
void deleteNode(int key)
{
     
    // Store head node
    Node temp = head, prev = null;
 
    // If head node itself holds the
    // key to be deleted
    if (temp != null && temp.data == key)
    {
         
        // Changed head
        head = temp.next;
        return;
    }
 
    // Search for the key to be deleted,
    // keep track of the previous node
    // as we need to change temp.next
    while (temp != null && temp.data != key)
    {
        prev = temp;
        temp = temp.next;
    }
 
    // If key was not present in linked list
    if (temp == null) return;
 
    // Unlink the node from linked list
    prev.next = temp.next;
}
 
// Function to delete all the nodes
// from linked list containing
// even numbers.
void deleteEvenNodes()
{
    Node ptr = head;
 
    // loop to iterate the linked list
    while(ptr != null)
    {
 
        // If containing element is even
        if(ptr.data % 2 == 0)
        {
             
            // Delete the node
            deleteNode(ptr.data);
        }
        ptr = ptr.next;
    }
}
 
// This function prints contents of linked
// list starting from the given node
public void printList()
{
    Node ptr = head;
    while (ptr != null)
    {
        System.out.print(ptr.data + "-> ");
        ptr = ptr.next;
    }
}
 
// Driver code
public static void main(String[] args)
{
    LinkedList head = new LinkedList();
 
    head.push(19);
    head.push(18);
    head.push(3);
    head.push(4);
    head.push(1);
 
    System.out.print("\nInitial List: ");
    head.printList();
 
    head.deleteEvenNodes();
 
    System.out.print("\nFinal List: ");
    head.printList();
}
}
 
// This code is contributed by Amit Mangal

Python3

# Python3 implementation to delete all
# even nodes from the singly linked list
# Node class
class Node:
     
    # Function to initialize the node object
    def __init__(self, data):
         
        # Assign data
        self.data = data
         
        # Initialize
        # next as null
        self.next = None
     
# Linked List Class
class LinkedList:
     
    # Function to initialize the
    # LinkedList class.
    def __init__(self):
 
        # Initialize head as None
        self.head = None
 
    # This function insert a new node at
    # the beginning of the linked list
    def push(self, new_data):
     
        # Create a new Node
        new_node = Node(new_data)
 
        # Make next of new Node as head
        new_node.next = self.head
 
        # Move the head to point to new Node
        self.head = new_node
         
    # Method to print the linked list
    def printList(self):
 
        # Object to iterate
        # the list
        ptr = self.head
 
        # Loop to iterate list
        while(ptr != None):
             
            print(ptr.data, '-> ', end = '')
 
            # Moving the iterating object
            # to next node
            ptr = ptr.next
             
        print()
 
    # Method to delete a node in
    # a singly linked list.
    def deleteNode(self, key):
        temp = self.head
 
        # If head node itself holds
        # the key to be deleted.
        if(temp != None and temp.data == key):
 
            # Changing head of list.
            self.head = temp.next
            return
 
        # Search for the key to be
        # deleted, keep track of the
        # previous node as we need
        # to change prev.next
        while(temp != None and temp.data != key):
            prev = temp
            temp = temp.next
 
        # If is not present in list
        if(temp == None):
            return
 
        # Unlink the node from
        # linked list
        prev.next = temp.next
 
    # Method to delete all the
    # even nodes from singly
    # linked list.
    def deleteEvenNodes(self):
        ptr = self.head
 
        # Loop to iterate the
        # linked list.
        while(ptr != None):
 
            # If node contains even number.
            if(ptr.data % 2 == 0):
 
                # Deleting the node
                self.deleteNode(ptr.data)
                 
            ptr = ptr.next
 
# Driver code
if __name__=='__main__':
 
    head = LinkedList()
     
    # Pushing elements at start
    # of linked list.
    head.push(19)
    head.push(18)
    head.push(3)
    head.push(4)
    head.push(1)
     
    # Print initial linked list
    print("Initial list: ", end = '')
    head.printList()
 
    # Calling the function to delete
    # nodes containing even numbers.
    head.deleteEvenNodes()
 
    # Print the final list
    print("Final list: ", end = '')
    head.printList()
     
# This code is contributed by Amit Mangal

C#

// C# implementation to delete all
// even nodes from the singly linked list
using System;
class List{
 
  // head of list
  Node head;
 
  // Linked list Node
  public class Node
  {
    public int data;
    public Node next;
    public Node(int d)
    {
      data = d;
      next = null;
    }
  }
 
  // Function to insert a node at
  // the beginning of the singly
  // Linked List
  public void push(int new_data)
  {
    Node new_node = new Node(new_data);
    new_node.next = head;
    head = new_node;
  }
 
  // Function to delete a node in a
  // singly Linked List.
  void deleteNode(int key)
  {    
    // Store head node
    Node temp = head, prev = null;
 
    // If head node itself holds the
    // key to be deleted
    if (temp != null &&
        temp.data == key)
    {        
      // Changed head
      head = temp.next;
      return;
    }
 
    // Search for the key to be deleted,
    // keep track of the previous node
    // as we need to change temp.next
    while (temp != null &&
           temp.data != key)
    {
      prev = temp;
      temp = temp.next;
    }
 
    // If key was not present
    // in linked list
    if (temp == null)
      return;
 
    // Unlink the node from
    // linked list
    prev.next = temp.next;
  }
 
  // Function to delete
  // all the nodes  from
  // linked list containing
  // even numbers.
  void deleteEvenNodes()
  {
    Node ptr = head;
 
    // loop to iterate the linked list
    while(ptr != null)
    {
      // If containing element is even
      if(ptr.data % 2 == 0)
      {            
        // Delete the node
        deleteNode(ptr.data);
      }
      ptr = ptr.next;
    }
  }
 
  // This function prints contents of linked
  // list starting from the given node
  public void printList()
  {
    Node ptr = head;
    while (ptr != null)
    {
      Console.Write(ptr.data + "-> ");
      ptr = ptr.next;
    }
  }
 
  // Driver code
  public static void Main(String []args)
  {
    List head = new List();
 
    head.push(19);
    head.push(18);
    head.push(3);
    head.push(4);
    head.push(1);
 
    Console.Write("\nInitial List: ");
    head.printList();
 
    head.deleteEvenNodes();
 
    Console.Write("\nFinal List: ");
    head.printList();
  }
}
  
// This code contributed by gauravrajput1

Javascript

// javascript implementation to delete all
// even nodes from the singly linked list
 
    // head of list
    var head;
 
    // Linked list Node
     class Node {
            constructor(val) {
                this.data = val;
                this.next = null;
            }
        }
 
    // Function to insert a node at
    // the beginning of the singly
    // Linked List
     function push(new_data) {
var new_node = new Node(new_data);
        new_node.next = head;
        head = new_node;
    }
 
    // Function to delete a node in a
    // singly Linked List.
    function deleteNode(key) {
 
        // Store head node
var temp = head, prev = null;
 
        // If head node itself holds the
        // key to be deleted
        if (temp != null && temp.data == key) {
 
            // Changed head
            head = temp.next;
            return;
        }
 
        // Search for the key to be deleted,
        // keep track of the previous node
        // as we need to change temp.next
        while (temp != null && temp.data != key) {
            prev = temp;
            temp = temp.next;
        }
 
        // If key was not present in linked list
        if (temp == null)
            return;
 
        // Unlink the node from linked list
        prev.next = temp.next;
    }
 
    // Function to delete all the nodes
    // from linked list containing
    // even numbers.
    function deleteEvenNodes() {
var ptr = head;
 
        // loop to iterate the linked list
        while (ptr != null) {
 
            // If containing element is even
            if (ptr.data % 2 == 0) {
 
                // Delete the node
                deleteNode(ptr.data);
            }
            ptr = ptr.next;
        }
    }
 
    // This function prints contents of linked
    // list starting from the given node
     function printList() {
var ptr = head;
        while (ptr != null) {
            document.write(ptr.data + "-> ");
            ptr = ptr.next;
        }
    }
 
    // Driver code
     
 
        push(19);
        push(18);
        push(3);
        push(4);
        push(1);
 
        document.write("<br/>Initial List: ");
        printList();
 
        deleteEvenNodes();
 
        document.write("<br/>Final List: ");
        printList();
 
// This code contributed by aashish1995

输出：

Initial List:  1 ->  4 ->  3 ->  18 ->  19 -> 
Final List:  1 ->  3 ->  19 ->

时间复杂度： O(N) ，其中 N 是节点总数。

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