Program to position even and odd nodes together - codeitwise

Here we are going to write a program to position even and odd nodes together. First we will create a linked list and then put all the even position nodes together then the odd position nodes together or vice-versa is also true.

Suppose,

Input - 1 => 2 => 3 => 4 => NULL

Output - 2 => 4 => 1 => 3 => NULL

OR

Output- 1 => 3 => 2 => 4 => NULL

Program to position even and odd nodes together-

C Code-

#include <stdio.h>
#include <malloc.h>

struct node{
    int data;
    struct node* next;
};

void create(struct node** head,int val){
    struct node* temp=*head;
    struct node* newnode=(struct node*)malloc(sizeof(struct node));
    newnode->data=val;
    newnode->next=NULL;
    if(*head==NULL){
        *head=newnode;
        return;
    }
    while(temp->next!=NULL){
        temp=temp->next;
    }
    temp->next=newnode;
}

struct node* evod(struct node* head){
    struct node* odd=head;
    struct node* even=head->next;
    struct node* evenfirst=even;
    if(head==NULL){
        return NULL;

    }
    while(1){
        odd->next=even->next;
        odd=even->next;
        if(odd->next==NULL)
        {
            even->next=NULL;
            odd->next=evenfirst;
            break;
        }
        even->next=odd->next;
        even=odd->next;
    }
    return head;
}
void display(struct node* head){
    while(head!=NULL){
        printf("%d => ",head->data);
        head=head->next;
    }
    printf("NULL\n");
}
int main(){
    struct node* head=NULL;
    create(&head,1);
    create(&head,2);
    create(&head,3);
    create(&head,4);
    create(&head,5);
    create(&head,6);
    create(&head,7);
    evenodd(&head);
    display(head);
    head=evod(head);
    display(head);
    return 0;
}

Output-

1 => 2 => 3 => 4 => 5 => 6 => 7 => NULL
1 => 3 => 5 => 7 => 2 => 4 => 6 => NULL

Time Complexity: O(n) where n is the length of the linked list.

Linked List Problems- 

• Count Number of Occurrence of given integer in Linked List

• Find Length of Loop in Linked List

• Delete Duplicate Elements from Sorted Linked List