删除循环链表的所有偶数节点

给定一个包含 N 个节点的循环单链表，任务是从列表中删除所有偶数节点。

例子：

Input : 57->11->2->56->12->61 
Output : List after deletion : 57 -> 11 -> 61 

Input : 9->11->32->6->13->20
Output : List after deletion : 9 -> 11 -> 13 

思路是逐个遍历循环单链表的节点，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。
下面是上述思想的实现：

C++

// CPP program to delete all even
// node from a Circular singly linked list
 
#include 
using namespace std;
 
// Structure for a node
struct Node {
    int data;
    struct Node* next;
};
 
// Function to insert a node at the beginning
// of a Circular linked list
void push(struct Node** head_ref, int data)
{
    struct Node* ptr1 = (struct Node*)malloc(sizeof(struct Node));
    struct Node* temp = *head_ref;
    ptr1->data = data;
    ptr1->next = *head_ref;
 
    // If linked list is not NULL then
    // set the next of last node
    if (*head_ref != NULL) {
        while (temp->next != *head_ref)
            temp = temp->next;
        temp->next = ptr1;
    }
    else
        ptr1->next = ptr1; // For the first node
 
    *head_ref = ptr1;
}
 
// Delete the node if it is even
void deleteNode(Node* head_ref, Node* del)
{
    struct Node* temp = head_ref;
    // If node to be deleted is head node
 
    if (head_ref == del)
        head_ref = del->next;
 
    // traverse list till not found
    // delete node
    while (temp->next != del) {
        temp = temp->next;
    }
 
    // copy address of node
    temp->next = del->next;
 
    // Finally, free the memory occupied by del
    free(del);
    return;
}
 
// Function to delete all even nodes
// from the singly circular  linked list
void deleteEvenNodes(Node* head)
{
    struct Node* ptr = head;
 
    struct Node* next;
 
    // traverse list till the end
    // if the node is even then delete it
    do {
        // if node is even
        if (ptr->data % 2 == 0)
            deleteNode(head, ptr);
 
        // point to next node
        next = ptr->next;
        ptr = next;
    } while (ptr != head);
}
 
// Function to print nodes
void printList(struct Node* head)
{
    struct Node* temp = head;
    if (head != NULL) {
        do {
            printf("%d ", temp->data);
            temp = temp->next;
        } while (temp != head);
    }
}
 
// Driver code
int main()
{
    // Initialize lists as empty
    struct Node* head = NULL;
 
    // Created linked list will be 57->11->2->56->12->61
    push(&head, 61);
    push(&head, 12);
    push(&head, 56);
    push(&head, 2);
    push(&head, 11);
    push(&head, 57);
 
    cout << "\nList after deletion : ";
    deleteEvenNodes(head);
    printList(head);
 
    return 0;
}

Java

// Java program to delete all prime
// node from a Circular singly linked list
class GFG
{
 
// Structure for a node
static class Node
{
    int data;
    Node next;
};
 
// Function to insert a node at the beginning
// of a Circular linked list
static Node push(Node head_ref, int data)
{
    Node ptr1 = new Node();
    Node temp = head_ref;
    ptr1.data = data;
    ptr1.next = head_ref;
 
    // If linked list is not null then
    // set the next of last node
    if (head_ref != null)
    {
        while (temp.next != head_ref)
            temp = temp.next;
        temp.next = ptr1;
        return head_ref;
    }
    else
        ptr1.next = ptr1; // For the first node
 
    head_ref = ptr1;
return head_ref;
}
 
// Delete the node if it is even
static Node deleteNode(Node head_ref, Node del)
{
    Node temp = head_ref;
    // If node to be deleted is head node
 
    if (head_ref == del)
        head_ref = del.next;
 
    // traverse list till not found
    // delete node
    while (temp.next != del)
    {
        temp = temp.next;
    }
 
    // copy address of node
    temp.next = del.next;
 
    return head_ref;
}
 
// Function to delete all even nodes
// from the singly circular linked list
static Node deleteEvenNodes(Node head)
{
    Node ptr = head;
 
    Node next;
 
    // traverse list till the end
    // if the node is even then delete it
    do
    {
        // if node is even
        if (ptr.data % 2 == 0)
            deleteNode(head, ptr);
 
        // point to next node
        next = ptr.next;
        ptr = next;
    }
    while (ptr != head);
    return head;
}
 
// Function to print nodes
static void printList(Node head)
{
    Node temp = head;
    if (head != null)
    {
        do
        {
            System.out.printf("%d ", temp.data);
            temp = temp.next;
        }
        while (temp != head);
    }
}
 
// Driver code
public static void main(String args[])
{
    // Initialize lists as empty
    Node head = null;
 
    // Created linked list will be 57.11.2.56.12.61
    head=push(head, 61);
    head=push(head, 12);
    head=push(head, 56);
    head=push(head, 2);
    head=push(head, 11);
    head=push(head, 57);
 
    System.out.println( "\nList after deletion : ");
    head=deleteEvenNodes(head);
    printList(head);
}
}
 
// This code is contributed by Arnab Kundu

Python3

# Python3 program to delete all even
# node from a Circular singly linked list
import math
 
# Structure for a node
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
 
# Function to insert a node at the beginning
# of a Circular linked list
def push(head_ref, data):
    ptr1 = Node(data)
    temp = head_ref
    ptr1.data = data
    ptr1.next = head_ref
 
    # If linked list is not None then
    # set the next of last node
    if (head_ref != None):
        while (temp.next != head_ref):
            temp = temp.next
        temp.next = ptr1
         
    else:
        ptr1.next = ptr1 # For the first node
 
    head_ref = ptr1
    return head_ref
 
# Delete the node if it is even
def deleteNode(head_ref, delete):
    temp = head_ref
     
    # If node to be deleted is head node
    if (head_ref == delete):
        head_ref = delete.next
 
    # traverse list till not found
    # delete node
    while (temp.next != delete):
        temp = temp.next
     
    # copy address of node
    temp.next = delete.next
     
    # Finally, free the memory occupied by delete
 
# Function to delete all even nodes
# from the singly circular linked list
def deleteEvenNodes(head):
    ptr = head
    next = None
 
    # traverse list till the end
    # if the node is even then delete it
    # if node is even
    next = ptr.next
    ptr = next
    while (ptr != head):
        if (ptr.data % 2 == 0):
            deleteNode(head, ptr)
 
        # point to next node
        next = ptr.next
        ptr = next
    return head
 
# Function to print nodes
def printList(head):
    temp = head
    if (head != None):
        print(temp.data, end = " ")
        temp = temp.next
        while (temp != head):
            print(temp.data, end = " ")
            temp = temp.next
         
# Driver code
if __name__=='__main__':
     
    # Initialize lists as empty
    head = None
 
    # Created linked list will be 57.11.2.56.12.61
    head = push(head, 61)
    head = push(head, 12)
    head = push(head, 56)
    head = push(head, 2)
    head = push(head, 11)
    head = push(head, 57)
 
    print("List after deletion : ", end = "")
    head = deleteEvenNodes(head)
    printList(head)
     
# This code is contributed by Srathore

C#

// C# program to delete all prime
// node from a Circular singly linked list
using System;
 
class GFG
{
 
// Structure for a node
public class Node
{
    public int data;
    public Node next;
};
 
// Function to insert a node at the beginning
// of a Circular linked list
static Node push(Node head_ref, int data)
{
    Node ptr1 = new Node();
    Node temp = head_ref;
    ptr1.data = data;
    ptr1.next = head_ref;
 
    // If linked list is not null then
    // set the next of last node
    if (head_ref != null)
    {
        while (temp.next != head_ref)
            temp = temp.next;
        temp.next = ptr1;
        return head_ref;
    }
    else
        ptr1.next = ptr1; // For the first node
 
    head_ref = ptr1;
return head_ref;
}
 
// Delete the node if it is even
static Node deleteNode(Node head_ref, Node del)
{
    Node temp = head_ref;
     
    // If node to be deleted is head node
    if (head_ref == del)
        head_ref = del.next;
 
    // traverse list till not found
    // delete node
    while (temp.next != del)
    {
        temp = temp.next;
    }
 
    // copy address of node
    temp.next = del.next;
 
    return head_ref;
}
 
// Function to delete all even nodes
// from the singly circular linked list
static Node deleteEvenNodes(Node head)
{
    Node ptr = head;
 
    Node next;
 
    // traverse list till the end
    // if the node is even then delete it
    do
    {
        // if node is even
        if (ptr.data % 2 == 0)
            deleteNode(head, ptr);
 
        // point to next node
        next = ptr.next;
        ptr = next;
    }
    while (ptr != head);
    return head;
}
 
// Function to print nodes
static void printList(Node head)
{
    Node temp = head;
    if (head != null)
    {
        do
        {
            Console.Write("{0} ", temp.data);
            temp = temp.next;
        }
        while (temp != head);
    }
}
 
// Driver code
public static void Main(String []args)
{
    // Initialize lists as empty
    Node head = null;
 
    // Created linked list will be 57.11.2.56.12.61
    head=push(head, 61);
    head=push(head, 12);
    head=push(head, 56);
    head=push(head, 2);
    head=push(head, 11);
    head=push(head, 57);
 
    Console.WriteLine( "\nList after deletion : ");
    head=deleteEvenNodes(head);
    printList(head);
}
}
 
// This code has been contributed by 29AjayKumar

Javascript

// javascript program to delete all prime
// node from a Circular singly linked list     // Structure for a node
class Node {
    constructor() {
        this.data = 0;
        this.next = null;
    }
}
 
    // Function to insert a node at the beginning
    // of a Circular linked list
    function push(head_ref , data) {
var ptr1 = new Node();
var temp = head_ref;
        ptr1.data = data;
        ptr1.next = head_ref;
 
        // If linked list is not null then
        // set the next of last node
        if (head_ref != null) {
            while (temp.next != head_ref)
                temp = temp.next;
            temp.next = ptr1;
            return head_ref;
        } else
            ptr1.next = ptr1; // For the first node
 
        head_ref = ptr1;
        return head_ref;
    }
 
    // Delete the node if it is even
    function deleteNode(head_ref,  del) {
var temp = head_ref;
        // If node to be deleted is head node
 
        if (head_ref == del)
            head_ref = del.next;
 
        // traverse list till not found
        // delete node
        while (temp.next != del) {
            temp = temp.next;
        }
 
        // copy address of node
        temp.next = del.next;
 
        return head_ref;
    }
 
    // Function to delete all even nodes
    // from the singly circular linked list
    function deleteEvenNodes(head) {
var ptr = head;
 
var next;
 
        // traverse list till the end
        // if the node is even then delete it
        do {
            // if node is even
            if (ptr.data % 2 == 0)
                deleteNode(head, ptr);
 
            // point to next node
            next = ptr.next;
            ptr = next;
        } while (ptr != head);
        return head;
    }
 
    // Function to print nodes
    function printList(head) {
var temp = head;
        if (head != null) {
            do {
                document.write( temp.data+" ");
                temp = temp.next;
            } while (temp != head);
        }
    }
 
    // Driver code
     
        // Initialize lists as empty
var head = null;
 
        // Created linked list will be 57.11.2.56.12.61
        head = push(head, 61);
        head = push(head, 12);
        head = push(head, 56);
        head = push(head, 2);
        head = push(head, 11);
        head = push(head, 57);
 
        document.write("\nList after deletion : ");
        head = deleteEvenNodes(head);
        printList(head);
 
// This code contributed by umadevi9616

输出：

List after deletion : 57 11 61

时间复杂度： O(N) ，其中 N 是节点的总数。