算法设计:如何检查两个相同的链表?

2021年3月18日14:46:11 发表评论 797 次浏览

本文概述

当两个链表具有相同的数据并且数据的排列也相同时, 它们是相同的。例如, 链接列表a(1-> 2-> 3)和b(1-> 2-> 3)相同。。编写一个函数来检查给定的两个链表是否相同。

推荐:请在"实践首先, 在继续解决方案之前。

方法1(迭代)

为了确定两个列表是否相同, 我们需要同时遍历两个列表, 并且在遍历时需要比较数据。

C ++

// An iterative C++ program to check if 
// two linked lists are identical or not
#include<bits/stdc++.h>
using namespace std;
  
/* Structure for a linked list node */
struct Node
{
     int data;
     struct Node *next;
};
  
/* Returns true if linked lists a and b 
are identical, otherwise false */
bool areIdentical( struct Node *a, struct Node *b)
{
     while (a != NULL && b != NULL)
     {
         if (a->data != b->data)
             return false ;
  
         /* If we reach here, then a and b are 
         not NULL and their data is same, so 
         move to next nodes in both lists */
         a = a->next;
         b = b->next;
     }
  
     // If linked lists are identical, then 
     // 'a' and 'b' must be NULL at this point.
     return (a == NULL && b == NULL);
}
  
/* UTILITY FUNCTIONS TO TEST fun1() and fun2() */
/* Given a reference (pointer to pointer) to the 
head of a list and an int, push a new node on the 
front of the list. */
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 = 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;
}
  
// Driver Code
int main()
{
     /* The constructed linked lists are :
     a: 3->2->1
     b: 3->2->1 */
     struct Node *a = NULL;
     struct Node *b = NULL;
     push(&a, 1);
     push(&a, 2);
     push(&a, 3);
     push(&b, 1);
     push(&b, 2);
     push(&b, 3);
  
     if (areIdentical(a, b))
         cout << "Identical" ;
     else
         cout << "Not identical" ;
  
     return 0;
}
  
// This code is contributed 
// by Akanksha Rai

C

// An iterative C program to check if two linked lists are
// identical or not
#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>
  
/* Structure for a linked list node */
struct Node
{
     int data;
     struct Node *next;
};
  
/* Returns true if linked lists a and b are identical, otherwise false */
bool areIdentical( struct Node *a, struct Node *b)
{
     while (a != NULL && b != NULL)
     {
         if (a->data != b->data)
             return false ;
  
         /* If we reach here, then a and b are not NULL and
            their data is same, so move to next nodes in both
            lists */
         a = a->next;
         b = b->next;
     }
  
     // If linked lists are identical, then 'a' and 'b' must
     // be NULL at this point.
     return (a == NULL && b == NULL);
}
  
/* UTILITY FUNCTIONS TO TEST fun1() and fun2() */
/* Given a reference (pointer to pointer) to the head
   of a list and an int, push a new node on the front
   of the list. */
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  = 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;
}
  
/* Driver program to test above function */
int main()
{
     /* The constructed linked lists are :
      a: 3->2->1
      b: 3->2->1 */
     struct Node *a = NULL;
     struct Node *b = NULL;
     push(&a, 1);
     push(&a, 2);
     push(&a, 3);
     push(&b, 1);
     push(&b, 2);
     push(&b, 3);
  
     areIdentical(a, b)? printf ( "Identical" ):
                         printf ( "Not identical" );
  
     return 0;
}

Java

// An iterative Java program to check if two linked lists
// are identical or not
class LinkedList
{
     Node head;  // head of list
  
     /* Linked list Node*/
     class Node
     {
         int data;
         Node next;
         Node( int d) { data = d; next = null ; }
     }
  
     /* Returns true if linked lists a and b are identical, otherwise false */
     boolean areIdentical(LinkedList listb)
     {
         Node a = this .head, b = listb.head;
         while (a != null && b != null )
         {
             if (a.data != b.data)
                 return false ;
  
             /* If we reach here, then a and b are not null
                and their data is same, so move to next nodes
                in both lists */
             a = a.next;
             b = b.next;
         }
  
         // If linked lists are identical, then 'a' and 'b' must
         // be null at this point.
         return (a == null && b == null );
     }
  
     /* UTILITY FUNCTIONS TO TEST fun1() and fun2() */
     /*  Given a reference (pointer to pointer) to the head
         of a list and an int, push a new node on the front
         of the list. */
  
     void push( int new_data)
     {
         /* 1 & 2: Allocate the Node &
                   Put in the data*/
         Node new_node = new Node(new_data);
  
         /* 3. Make next of new Node as head */
         new_node.next = head;
  
         /* 4. Move the head to point to new Node */
         head = new_node;
     }
  
  
     /* Driver program to test above functions */
     public static void main(String args[])
     {
         LinkedList llist1 = new LinkedList();
         LinkedList llist2 = new LinkedList();
  
         /* The constructed linked lists are :
            llist1: 3->2->1
            llist2: 3->2->1 */
  
         llist1.push( 1 );
         llist1.push( 2 );
         llist1.push( 3 );
  
         llist2.push( 1 );
         llist2.push( 2 );
         llist2.push( 3 );
  
         if (llist1.areIdentical(llist2) == true )
             System.out.println( "Identical " );
         else
             System.out.println( "Not identical " );
  
     }
} /* This code is contributed by Rajat Mishra */

Python3

# An iterative Java program to check if 
# two linked lists are identical or not 
  
# Linked list Node 
class Node: 
     def __init__( self , d):
         self .data = d
         self . next = None
  
class LinkedList:
     def __init__( self ):
         self .head = None # head of list 
      
     # Returns true if linked lists a and b
     # are identical, otherwise false 
     def areIdentical( self , listb): 
         a = self .head
         b = listb.head
         while (a ! = None and b ! = None ): 
             if (a.data ! = b.data): 
                 return False
  
             # If we reach here, then a and b 
             # are not null and their data is 
             # same, so move to next nodes 
             # in both lists 
             a = a. next
             b = b. next
  
         # If linked lists are identical, # then 'a' and 'b' must be null
         # at this point. 
         return (a = = None and b = = None ) 
  
     # UTILITY FUNCTIONS TO TEST fun1() and fun2() 
     # Given a reference (pointer to pointer) to the 
     # head of a list and an int, push a new node on 
     # the front of the list. 
  
     def push( self , new_data):
          
         # 1 & 2: Allocate the Node & 
         # Put in the data
         new_node = Node(new_data) 
  
         # 3. Make next of new Node as head 
         new_node. next = self .head 
  
         # 4. Move the head to point to new Node 
         self .head = new_node
  
# Driver Code
llist1 = LinkedList() 
llist2 = LinkedList() 
  
# The constructed linked lists are : 
# llist1: 3->2->1 
# llist2: 3->2->1 
llist1.push( 1 ) 
llist1.push( 2 ) 
llist1.push( 3 ) 
llist2.push( 1 ) 
llist2.push( 2 ) 
llist2.push( 3 ) 
  
if (llist1.areIdentical(llist2) = = True ): 
     print ( "Identical " )
else :
     print ( "Not identical " )
  
# This code is contributed by Prerna Saini

C#

// An iterative C# program to 
// check if two linked lists
// are identical or not
using System;
      
public class LinkedList
{
     Node head; // head of list
  
     /* Linked list Node*/
     public class Node
     {
         public int data;
         public Node next;
         public Node( int d) 
         {
             data = d; next = null ; 
         }
     }
  
     /* Returns true if linked lists 
     a and b are identical, otherwise false */
     bool areIdentical(LinkedList listb)
     {
         Node a = this .head, b = listb.head;
         while (a != null && b != null )
         {
             if (a.data != b.data)
                 return false ;
  
             /* If we reach here, then a and b are not null
             and their data is same, so move to next nodes
             in both lists */
             a = a.next;
             b = b.next;
         }
  
         // If linked lists are identical, // then 'a' and 'b' must
         // be null at this point.
         return (a == null && b == null );
     }
  
     /* UTILITY FUNCTIONS TO TEST fun1() and fun2() */
     /* Given a reference (pointer to pointer) to the head
         of a list and an int, push a new node on the front
         of the list. */
  
     void push( int new_data)
     {
         /* 1 & 2: Allocate the Node &
                 Put in the data*/
         Node new_node = new Node(new_data);
  
         /* 3. Make next of new Node as head */
         new_node.next = head;
  
         /* 4. Move the head to point to new Node */
         head = new_node;
     }
  
  
     /* Driver code */
     public static void Main(String []args)
     {
         LinkedList llist1 = new LinkedList();
         LinkedList llist2 = new LinkedList();
  
         /* The constructed linked lists are :
         llist1: 3->2->1
         llist2: 3->2->1 */
  
         llist1.push(1);
         llist1.push(2);
         llist1.push(3);
  
         llist2.push(1);
         llist2.push(2);
         llist2.push(3);
  
         if (llist1.areIdentical(llist2) == true )
             Console.WriteLine( "Identical " );
         else
             Console.WriteLine( "Not identical " );
     }
}
  
// This code contributed by Rajput-Ji

输出如下:

Identical

方法2(递归)

递归解决方案代码比迭代代码干净得多。但是, 你可能不希望将递归版本用于生产代码, 因为它会使用与列表长度成比例的堆栈空间

C ++

// A recursive C++ function to check if two linked 
// lists are identical or not 
bool areIdentical(Node *a, Node *b) 
{ 
     // If both lists are empty 
     if (a == NULL && b == NULL) 
     return true ; 
  
     // If both lists are not empty, then data of 
     // current nodes must match, and same should 
     // be recursively true for rest of the nodes. 
     if (a != NULL && b != NULL) 
     return (a->data == b->data) && 
             areIdentical(a->next, b->next); 
  
     // If we reach here, then one of the lists 
     // is empty and other is not 
     return false ; 
} 
  
//This is code is contributed by rathbhupendra

C

// A recursive C function to check if two linked
// lists are identical or not
bool areIdentical( struct Node *a, struct Node *b)
{
     // If both lists are empty
     if (a == NULL && b == NULL)
        return true ;
  
     // If both lists are not empty, then data of
     // current nodes must match, and same should
     // be recursively true for rest of the nodes.
     if (a != NULL && b != NULL)
        return (a->data == b->data) &&
               areIdentical(a->next, b->next);
  
     // If we reach here, then one of the lists
     // is empty and other is not
     return false ;
}

Java

// A recursive Java method to check if two linked
// lists are identical or not
boolean areIdenticalRecur(Node a, Node b)
{
     // If both lists are empty
     if (a == null && b == null )
         return true ;
  
     // If both lists are not empty, then data of
     // current nodes must match, and same should
     // be recursively true for rest of the nodes.
     if (a != null && b != null )
         return (a.data == b.data) &&
                areIdenticalRecur(a.next, b.next);
  
     // If we reach here, then one of the lists
     // is empty and other is not
     return false ;
}
  
/* Returns true if linked lists a and b are identical, otherwise false */
boolean areIdentical(LinkedList listb)
{
     return areIdenticalRecur( this .head, listb.head);
}

Python3

# A recursive Python3 function to check 
# if two linked lists are identical or not 
def areIdentical(a, b): 
      
     # If both lists are empty 
     if (a = = None and b = = None ): 
         return True
  
     # If both lists are not empty, # then data of current nodes must match, # and same should be recursively true 
     # for rest of the nodes. 
     if (a ! = None and b ! = None ): 
         return ((a.data = = b.data) and 
                  areIdentical(a. next , b. next )) 
  
     # If we reach here, then one of the lists 
     # is empty and other is not 
     return False
  
# This code is contributed by Princi Singh

C#

// A recursive C# method to 
// check if two linked lists 
// are identical or not 
bool areIdenticalRecur(Node a, Node b) 
{ 
     // If both lists are empty 
     if (a == null && b == null ) 
         return true ; 
  
     // If both lists are not empty, then data of 
     // current nodes must match, and same should 
     // be recursively true for rest of the nodes. 
     if (a != null && b != null ) 
         return (a.data == b.data) && 
             areIdenticalRecur(a.next, b.next); 
  
     // If we reach here, then one of the lists 
     // is empty and other is not 
     return false ; 
} 
  
/* Returns true if linked lists 
a and b are identical, otherwise false */
bool areIdentical(LinkedList listb) 
{ 
     return areIdenticalRecur( this .head, listb.head); 
} 
}
  
// This code is contributed by princiraj1992

时间复杂度:迭代和递归版本均为O(n)。 n是a和b中较小列表的长度。

如果你发现上述代码/算法有误, 请写评论, 或者找到解决同一问题的更好方法。

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