算法设计（以给定大小的组反向链表|套装2） _反向链表

本文概述

建议：在继续解决方案之前, 请先在"实践"上解决它。
C ++
Java
Python3
C#

给定一个链表, 编写一个函数以反转每k个节点(其中k是该函数的输入)。
例子：

Inputs:1-> 2-> 3-> 4-> 5-> 6-> 7-> 8-> NULL and k = 3 Output:3-> 2-> 1-> 6-> 5-> 4-> 8-> 7-> NULL. Inputs:1-> 2-> 3-> 4-> 5-> 6-> 7-> 8-> NULL and k = 5Output:5-> 4-> 3-> 2-> 1-> 8-> 7-> 6-> NULL.

推荐：请在"实践首先, 在继续解决方案之前。我们已经在下面的帖子中讨论了其解决方案
以给定大小的组反向链接列表|套装1
在本文中, 我们使用了一个堆栈, 该堆栈将存储给定链接列表的节点。首先, 将链接列表的k个元素压入堆栈。现在一个接一个地弹出元素, 并跟踪先前弹出的节点。将上一个节点的下一个指针指向堆栈的顶部元素。重复此过程, 直到达到NULL。
该算法使用O(k)额外空间。
C ++

// C++ program to reverse a linked list in groups // of given size #include < bits/stdc++.h> using namespace std; /* Link list node */ struct Node { int data; struct Node* next; }; /* Reverses the linked list in groups of size k and returns the pointer to the new head node. */ struct Node* Reverse( struct Node* head, int k) { // Create a stack of Node* stack< Node*> mystack; struct Node* current = head; struct Node* prev = NULL; while (current != NULL) {// Terminate the loop whichever comes first // either current == NULL or count > = k int count = 0; while (current != NULL & & count < k) { mystack.push(current); current = current-> next; count++; }// Now pop the elements of stack one by one while (mystack.size() > 0) {// If final list has not been started yet. if (prev == NULL) { prev = mystack.top(); head = prev; mystack.pop(); } else { prev-> next = mystack.top(); prev = prev-> next; mystack.pop(); } } }// Next of last element will point to NULL. prev-> next = NULL; return head; }/* UTILITY FUNCTIONS */ /* Function to push a node */ void push( struct Node** head_ref, int new_data) { /* allocate node */ struct Node* new_node = ( struct Node*) malloc ( sizeof ( struct Node)); /* put in the data*/ new_node-> data = https://www.lsbin.com/new_data; /* link the old list off the new node */ new_node-> next = (*head_ref); /* move the head to point to the new node */ (*head_ref) = new_node; }/* Function to print linked list */ void printList( struct Node* node) { while (node != NULL) { printf ("%d" , node-> data); node = node-> next; } }/* Driver program to test above function*/ int main( void ) { /* Start with the empty list */ struct Node* head = NULL; /* Created Linked list is 1-> 2-> 3-> 4-> 5-> 6-> 7-> 8-> 9 */ push(& head, 9); push(& head, 8); push(& head, 7); push(& head, 6); push(& head, 5); push(& head, 4); push(& head, 3); push(& head, 2); push(& head, 1); printf ( "\nGiven linked list \n" ); printList(head); head = Reverse(head, 3); printf ( "\nReversed Linked list \n" ); printList(head); return 0; }

Java

// Java program to reverse a linked list in groups // of given size import java.util.*; class GfG {/* Link list node */ static class Node { int data; Node next; } static Node head = null ; /* Reverses the linked list in groups of size k and returns the pointer to the new head node. */ static Node Reverse(Node head, int k) { // Create a stack of Node* Stack< Node> mystack = new Stack< Node> (); Node current = head; Node prev = null ; while (current != null ) { // Terminate the loop whichever comes first // either current == NULL or count > = k int count = 0 ; while (current != null & & count < k) { mystack.push(current); current = current.next; count++; } // Now pop the elements of stack one by one while (mystack.size() > 0 ) { // If final list has not been started yet. if (prev == null ) { prev = mystack.peek(); head = prev; mystack.pop(); } else { prev.next = mystack.peek(); prev = prev.next; mystack.pop(); } } } // Next of last element will point to NULL. prev.next = null ; return head; } /* UTILITY FUNCTIONS */ /* Function to push a node */ static void push( int new_data) { /* allocate node */ Node new_node = new Node(); /* put in the data */ new_node.data = https://www.lsbin.com/new_data; /* link the old list off the new node */ new_node.next = head; /* move the head to point to the new node */ head = new_node; } /* Function to print linked list */ static void printList(Node node) { while (node != null ) { System.out.print(node.data +" " ); node = node.next; } } /* Driver code*/ public static void main(String[] args) { /* Start with the empty list */ //Node head = null; /* Created Linked list is 1-> 2-> 3-> 4-> 5-> 6-> 7-> 8-> 9 */ push( 9 ); push( 8 ); push( 7 ); push( 6 ); push( 5 ); push( 4 ); push( 3 ); push( 2 ); push( 1 ); System.out.println( "Given linked list " ); printList(head); head = Reverse(head, 3 ); System.out.println(); System.out.println( "Reversed Linked list " ); printList(head); } } // This code is contributed by Prerna Saini

Python3

# Python3 program to reverse a Linked List # in groups of given size# Node class class Node( object ): __slots__ = 'data' , 'next'# Constructor to initialize the node object def __init__( self , data = https://www.lsbin.com/None , next = None ): self .data = data self . next = nextdef __repr__( self ): return repr ( self .data)class LinkedList( object ):# Function to initialize head def __init__( self ): self .head = None# Utility function to print nodes # of LinkedList def __repr__( self ): nodes = [] curr = self .head while curr: nodes.append( repr (curr)) curr = curr. next return'[' + ', ' .join(nodes) + ']'# Function to insert a new node at # the beginning def prepend( self , data): self .head = Node(data = https://www.lsbin.com/data, next = self .head)# Reverses the linked list in groups of size k # and returns the pointer to the new head node. def reverse( self , k = 1 ): if self .head is None : returncurr = self .head prev = None new_stack = [] while curr is not None : val = 0# Terminate the loop whichever comes first # either current == None or value > = k while curr is not None and val < k: new_stack.append(curr.data) curr = curr. next val + = 1# Now pop the elements of stack one by one while new_stack:# If final list has not been started yet. if prev is None : prev = Node(new_stack.pop()) self .head = prev else : prev. next = Node(new_stack.pop()) prev = prev. next# Next of last element will point to None. prev. next = None return self .head# Driver Code llist = LinkedList() llist.prepend( 9 ) llist.prepend( 8 ) llist.prepend( 7 ) llist.prepend( 6 ) llist.prepend( 5 ) llist.prepend( 4 ) llist.prepend( 3 ) llist.prepend( 2 ) llist.prepend( 1 )print ("Given linked list" ) print (llist) llist.head = llist.reverse( 3 )print ( "Reversed Linked list" ) print (llist)# This code is contributed by # Sagar Kumar Sinha(sagarsinha7777)

// C# program to reverse a linked list // in groups of given size using System; using System.Collections; class GfG { /* Link list node */ public class Node { public int data; public Node next; } static Node head = null ; /* Reverses the linked list in groups of size k and returns the pointer to the new head node. */ static Node Reverse(Node head, int k) { // Create a stack of Node* Stack mystack = new Stack(); Node current = head; Node prev = null ; while (current != null ) { // Terminate the loop whichever comes first // either current == NULL or count > = k int count = 0; while (current != null & & count < k) { mystack.Push(current); current = current.next; count++; } // Now Pop the elements of stack one by one while (mystack.Count > 0) { // If final list has not been started yet. if (prev == null ) { prev = (Node)mystack.Peek(); head = prev; mystack.Pop(); } else { prev.next = (Node)mystack.Peek(); prev = prev.next; mystack.Pop(); } } } // Next of last element will point to NULL. prev.next = null ; return head; } /* UTILITY FUNCTIONS */ /* Function to Push a node */ static void Push( int new_data) { /* allocate node */ Node new_node = new Node(); /* put in the data */ new_node.data = https://www.lsbin.com/new_data; /* link the old list off the new node */ new_node.next = head; /* move the head to point to the new node */ head = new_node; } /* Function to print linked list */ static void printList(Node node) { while (node != null ) { Console.Write(node.data +" " ); node = node.next; } } /* Driver code*/ public static void Main(String []args) { /* Start with the empty list */ //Node head = null; /* Created Linked list is 1-> 2-> 3-> 4-> 5-> 6-> 7-> 8-> 9 */ Push( 9); Push( 8); Push( 7); Push( 6); Push( 5); Push(4); Push(3); Push(2); Push( 1); Console.WriteLine( "Given linked list " ); printList(head); head = Reverse(head, 3); Console.WriteLine(); Console.WriteLine( "Reversed Linked list " ); printList(head); } } // This code is contributed by Arnab Kundu

输出如下：