删除链表的每个第 k 个节点

给定一个单链表，你的任务是删除链表的每个第 K 个节点。假设 K 总是小于或等于链表的长度。
例子 ：

Input : 1->2->3->4->5->6->7->8  
        k = 3
Output : 1->2->4->5->7->8
As 3 is the k-th node after its deletion list 
would be 1->2->4->5->6->7->8
And now 4 is the starting node then from it, 6 
would be the k-th node. So no other kth node 
could be there.So, final list is:
1->2->4->5->7->8.

Input: 1->2->3->4->5->6  
       k = 1
Output: Empty list 
All nodes need to be deleted

这个想法是从头开始遍历列表并跟踪最后一次删除后访问过的节点。每当计数变为 k 时，删除当前节点并将计数重置为 0。

(1) Traverse list and do following
   (a) Count node before deletion.
   (b) If (count == k) that means current 
        node is to be deleted.
      (i)  Delete current node i.e. do

          //  assign address of next node of 
          // current node to the previous node
          // of the current node.
          prev->next = ptr->next i.e.

       (ii) Reset count as 0, i.e., do count = 0.
   (c) Update prev node if count != 0 and if
       count is 0 that means that node is a
       starting point.
   (d) Update ptr and continue until all 
       k-th node gets deleted.

下面是实现。

C++

// C++ program to delete every k-th Node of
// a singly linked list.
#include
using namespace std;
 
/* Linked list Node */
struct Node
{
    int data;
    struct Node* next;
};
 
// To remove complete list (Needed for
// case when k is 1)
void freeList(Node *node)
{
    while (node != NULL)
    {
        Node *next = node->next;
        delete (node);
        node  = next;
    }
}
 
// Deletes every k-th node and returns head
// of modified list.
Node *deleteKthNode(struct Node *head, int k)
{
    // If linked list is empty
    if (head == NULL)
        return NULL;
 
    if (k == 1)
    {
       freeList(head);
       return NULL;
    }
 
    // Initialize ptr and prev before starting
    // traversal.
    struct Node *ptr = head, *prev = NULL;
 
    // Traverse list and delete every k-th node
    int count = 0;
    while (ptr != NULL)
    {
        // increment Node count
        count++;
 
        // check if count is equal to k
        // if yes, then delete current Node
        if (k == count)
        {
            // put the next of current Node in
            // the next of previous Node
            delete(prev->next);
            prev->next = ptr->next;
 
            // set count = 0 to reach further
            // k-th Node
            count = 0;
        }
 
        // update prev if count is not 0
        if (count != 0)
            prev = ptr;
 
        ptr = prev->next;
    }
 
    return head;
}
 
/* Function to print linked list */
void displayList(struct Node *head)
{
    struct Node *temp = head;
    while (temp != NULL)
    {
        cout<data<<" ";
        temp = temp->next;
    }
}
 
// Utility function to create a new node.
struct Node *newNode(int x)
{
    Node *temp = new Node;
    temp->data = x;
    temp->next = NULL;
    return temp;
}
 
/* Driver program to test count function*/
int main()
{
    /* Start with the empty list */
    struct 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(6);
    head->next->next->next->next->next->next =
                                        newNode(7);
    head->next->next->next->next->next->next->next =
                                        newNode(8);
 
    int k = 3;
    head = deleteKthNode(head, k);
 
    displayList(head);
 
    return 0;
}

Java

// Java program to delete every k-th Node
// of a singly linked list.
class GFG
{
 
/* Linked list Node */
static class Node
{
    int data;
    Node next;
}
 
// To remove complete list (Needed for
// case when k is 1)
static Node freeList(Node node)
{
    while (node != null)
    {
        Node next = node.next;
        node = next;
    }
    return node;
}
 
// Deletes every k-th node and
// returns head of modified list.
static Node deleteKthNode(Node head, int k)
{
    // If linked list is empty
    if (head == null)
        return null;
 
    if (k == 1)
    {
        head = freeList(head);
        return null;
    }
 
    // Initialize ptr and prev before
    // starting traversal.
    Node ptr = head, prev = null;
 
    // Traverse list and delete
    // every k-th node
    int count = 0;
    while (ptr != null)
    {
        // increment Node count
        count++;
 
        // check if count is equal to k
        // if yes, then delete current Node
        if (k == count)
        {
            // put the next of current Node in
            // the next of previous Node
            prev.next = ptr.next;
 
            // set count = 0 to reach further
            // k-th Node
            count = 0;
        }
 
        // update prev if count is not 0
        if (count != 0)
            prev = ptr;
 
        ptr = prev.next;
    }
    return head;
}
 
/* Function to print linked list */
static void displayList(Node head)
{
    Node temp = head;
    while (temp != null)
    {
        System.out.print(temp.data + " ");
        temp = temp.next;
    }
}
 
// Utility function to create a new node.
static Node newNode(int x)
{
    Node temp = new Node();
    temp.data = x;
    temp.next = null;
    return temp;
}
 
// 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(4);
    head.next.next.next.next = newNode(5);
    head.next.next.next.next.next = newNode(6);
    head.next.next.next.next.next.next =
                                        newNode(7);
    head.next.next.next.next.next.next.next =
                                        newNode(8);
 
    int k = 3;
    head = deleteKthNode(head, k);
 
    displayList(head);
}
}
 
// This code is contributed by Arnab Kundu

Python3

# Python3 program to delete every k-th Node
# of a singly linked list.
import math
 
# Linked list Node
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
 
# To remove complete list (Needed for
# case when k is 1)
def freeList(node):
    while (node != None):
        next = node.next
        node = next
    return node
 
# Deletes every k-th node and
# returns head of modified list.
def deleteKthNode(head, k):
     
    # If linked list is empty
    if (head == None):
        return None
 
    if (k == 1):
        freeList(head)
        return None
     
    # Initialize ptr and prev before
    # starting traversal.
    ptr = head
    prev = None
 
    # Traverse list and delete every k-th node
    count = 0
    while (ptr != None):
         
        # increment Node count
        count = count + 1
 
        # check if count is equal to k
        # if yes, then delete current Node
        if (k == count):
             
            # put the next of current Node in
            # the next of previous Node
            # delete(prev.next)
            prev.next = ptr.next
 
            # set count = 0 to reach further
            # k-th Node
            count = 0
         
        # update prev if count is not 0
        if (count != 0):
            prev = ptr
 
        ptr = prev.next
     
    return head
 
# Function to print linked list
def displayList(head):
    temp = head
    while (temp != None):
        print(temp.data, end = ' ')
        temp = temp.next
     
# Utility function to create a new node.
def newNode( x):
    temp = Node(x)
    temp.data = x
    temp.next = None
    return temp
 
# Driver Code
if __name__=='__main__':
     
    # Start with the empty list
    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(6)
    head.next.next.next.next.next.next = newNode(7)
    head.next.next.next.next.next.next.next = newNode(8)
 
    k = 3
    head = deleteKthNode(head, k)
 
    displayList(head)
 
# This code is contributed by Srathore

C#

// C# program to delete every k-th Node
// of a singly linked list.
using System;
     
class GFG
{
 
/* Linked list Node */
public class Node
{
    public int data;
    public Node next;
}
 
// To remove complete list (Needed for
// case when k is 1)
static Node freeList(Node node)
{
    while (node != null)
    {
        Node next = node.next;
        node = next;
    }
    return node;
}
 
// Deletes every k-th node and
// returns head of modified list.
static Node deleteKthNode(Node head, int k)
{
    // If linked list is empty
    if (head == null)
        return null;
 
    if (k == 1)
    {
        head = freeList(head);
        return null;
    }
 
    // Initialize ptr and prev before
    // starting traversal.
    Node ptr = head, prev = null;
 
    // Traverse list and delete
    // every k-th node
    int count = 0;
    while (ptr != null)
    {
        // increment Node count
        count++;
 
        // check if count is equal to k
        // if yes, then delete current Node
        if (k == count)
        {
            // put the next of current Node in
            // the next of previous Node
            prev.next = ptr.next;
 
            // set count = 0 to reach further
            // k-th Node
            count = 0;
        }
 
        // update prev if count is not 0
        if (count != 0)
            prev = ptr;
 
        ptr = prev.next;
    }
    return head;
}
 
/* Function to print linked list */
static void displayList(Node head)
{
    Node temp = head;
    while (temp != null)
    {
        Console.Write(temp.data + " ");
        temp = temp.next;
    }
}
 
// Utility function to create a new node.
static Node newNode(int x)
{
    Node temp = new Node();
    temp.data = x;
    temp.next = null;
    return temp;
}
 
// 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(4);
    head.next.next.next.next = newNode(5);
    head.next.next.next.next.next = newNode(6);
    head.next.next.next.next.next.next = newNode(7);
    head.next.next.next.next.next.next.next = newNode(8);
 
    int k = 3;
    head = deleteKthNode(head, k);
 
    displayList(head);
}
}
 
// This code is contributed by PrinciRaj1992

Javascript

 
// Javascript program to delete every k-th Node
// of a singly linked list.
/* Linked list Node */
class Node {
    constructor() {
        this.data = 0;
        this.next = null;
    }
}
 
 
    // To remove complete list (Needed for
    // case when k is 1)
    function freeList( node) {
        while (node != null) {
             next = node.next;
            node = next;
        }
        return node;
    }
 
    // Deletes every k-th node and
    // returns head of modified list.
    function deleteKthNode( head , k) {
        // If linked list is empty
        if (head == null)
            return null;
 
        if (k == 1) {
            head = freeList(head);
            return null;
        }
 
        // Initialize ptr and prev before
        // starting traversal.
        var ptr = head, prev = null;
 
        // Traverse list and delete
        // every k-th node
        var count = 0;
        while (ptr != null) {
            // increment Node count
            count++;
 
            // check if count is equal to k
            // if yes, then delete current Node
            if (k == count) {
                // put the next of current Node in
                // the next of previous Node
                prev.next = ptr.next;
 
                // set count = 0 to reach further
                // k-th Node
                count = 0;
            }
 
            // update prev if count is not 0
            if (count != 0)
                prev = ptr;
 
            ptr = prev.next;
        }
        return head;
    }
 
    /* Function to prvar linked list */
    function displayList( head) {
         temp = head;
        while (temp != null) {
            document.write(temp.data + " ");
            temp = temp.next;
        }
    }
 
    // Utility function to create a new node.
    function newNode(x) {
         temp = new Node();
        temp.data = x;
        temp.next = null;
        return temp;
    }
 
    // Driver Code
     
        /* Start with the empty list */
         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(6);
        head.next.next.next.next.next.next = newNode(7);
        head.next.next.next.next.next.next.next = newNode(8);
 
        var k = 3;
        head = deleteKthNode(head, k);
 
        displayList(head);
 
// This code contributed by umadevi9616
 

输出：

1 2 4 5 7 8

时间复杂度：O(n)

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