DATA STRUCTURES IN C – LINKED LIST (20 PROGRAMS)

Linked List in C – Split a Linked List into 2 Separate Linked List :

Input:
        Head Pointer: head
        Original linked list: node 1->node 2->node 3->node 4->node 5->node 6->node 7

Output:
        Head Pointer: head_of_list_1
        Linked List 1: node 1->node 3->node 5->node 7

        Head Pointer: head_of_list_2
        Linked List 2: node 2->node 4->node 6

Source Code :

#include<stdio.h>
struct node
{
    	//Structure named node to store integer in variable data and a pointer variable which can store address location of next node
    	int data;
    	struct node *next;
    	//Pointer variable next is a self referential pointer which stores the address of structure node
};
struct node *head = NULL;
//Pointer head is used to store the starting node of the input linked list

struct node *head_of_list_1 = NULL;
struct node *head_of_list_2 = NULL;
//Pointer head_of_list_1 and head_of_list_2 i used to store the starting node of the two output linked list
//Declared as global variable since it is accessed by multiple functions

void split_the_linked_list()
{
    	//Function to split a linked list into two seperate linked list
    	//If the original list is 1->2->3->4->5->6, then the the first linked list will contain nodes 1->3->5(outputlinked list 1)
    	//													 the seconf linked list will contain nodes 2->4->6(outputlinked list 2)

    	struct node *temp = head;	
    	//Use a new pointer variable temp
    	//Do not use the pointer variable head directly. If we use it, the address location of the first node in the linked list will be lost

    	struct node *listholder1 = NULL;
    	struct node *listholder2 = NULL;
    	//listholder1 and listholder2 are temporary pointer variables to store the address of last node of two output linked  list

    	struct node *ptr;	
    	int i=1;
    	while(temp!=NULL)
    	{
        		//Loop to traverse the original linked list
        		if(i%2==1)
        		{
            			//Executed for nodes with odd index of nodes i.e. for nodes 1,3,5 etc of the original input linked list
            			ptr = (struct node*)malloc(sizeof(struct node));
            			//A new node is created

            			ptr->data=temp->data;
           			 ptr->next=NULL;	
            			//The newly created node is assigned the data from the node of original list

            			if(head_of_list_1==NULL)
            			{						
               				//Executed only once when the the pointer head_of_list_1 is empty
				head_of_list_1=ptr;			
            			}
            			else
            			{			
                				listholder1->next=ptr;
                				//listholer1 is used to identify the last node of output linked list 1
                				//Once a new node is created we need to make listholder1 point to newly created node
            			}
            			listholder1=ptr;
            			//Making the newly created node as last node
        		}
        		else
        		{
            			//Executed for nodes with even index of nodes i.e. for nodes 2,4,6 etc of the original input linked list
            			//Other statements are same as above except that we use head_of_list_2 and listholder2 to maintain output linked list 2
            			ptr = (struct node*)malloc(sizeof(struct node));	
            			ptr->data=temp->data;
            			ptr->next=NULL;			
            			if(head_of_list_2==NULL)
            			{						
                				head_of_list_2=ptr;
            			}	
            			else
            			{
                				listholder2->next=ptr;
            			}
            			listholder2=ptr;
        		}
        		temp=temp->next;
        		i++;
    	}	
}

void print(struct node *temp)
{
    	//This funtion is used to print the data in each of the node in the linked list
    	//Process of moving from one node to another node is called as traversing
    	while(temp!=NULL)
    	{
        		printf("\n%d ",temp->data);
        		temp=temp->next;		
    	}	
}

int main()
{
    	struct node *one = (struct node*)malloc(sizeof(struct node));
    	struct node *two = (struct node*)malloc(sizeof(struct node));
    	struct node *three = (struct node*)malloc(sizeof(struct node));
    	struct node *four = (struct node*)malloc(sizeof(struct node));
    	struct node *five = (struct node*)malloc(sizeof(struct node));
    	struct node *six = (struct node*)malloc(sizeof(struct node));
    	struct node *seven = (struct node*)malloc(sizeof(struct node));
    	//Seven nodes are created

    	head=one;
    	//head pointsto node one of input linked list

    	one->data=1;
    	one->next=two;

    	two->data=2;	
    	two->next=three;

    	three->data=3;
    	three->next=four;

    	four->data=4;
    	four->next=five;

    	five->data=5;
    	five->next=six;

    	six->data=6;
    	six->next=seven;

    	seven->data=7;
    	seven->next=NULL;
    	//Last node of input linked list

    	//one->two->three->four->five->six->seven

    	split_the_linked_list();
    	//Function to split the input linked list into two output linked list

    	printf("\nOriginal Linked List/Input Linked List");
        	print(head);
    	//Printnig original linked list/input linked list

    	printf("\nOutput:Linked List 1");
    	print(head_of_list_1);
    	//Printnig output linked list 1

    	printf("\nOutput:Linked List 2");
	    print(head_of_list_2);
    	//Printnig output linked list 2

    	return 0;
}

Output :

Original Linked List/Input Linked List
1
2
3
4
5
6
7

Output:Linked List 1
1
3
5
7

Output:Linked List 2
2
4
6