Reverse a linked list using C

By Arjun Tyagi

In this article, we will discuss the method and program to reverse a linked list using the C programming language.

Reversing a linked-list:

A reverse  linked list is formed by changing the links between the nodes of a linked list.The head node of the linked list will be the last node of the linked list and the last one will be the head node. 

 

Time Complexity:

The time complexity to reverse a linked list is big-oh(n) or O(n) because we have traverse through the whole list one by one.

 

CODE:

#include 
#include
struct node{
    int data;
    struct node* next;
};                    //declaring a node data-type//

struct node* head;

void insertion(int data){
    struct node* newnode=(struct node*) malloc(sizeof(struct node));//allocating memory for a node//
    newnode->data=data;
    newnode->next=NULL;
    
    if(head==NULL){  //list is empty //
        head=newnode;
       
    }
    else{
        struct node* temp=head;
        while(temp->next!=NULL){
            temp=temp->next; //traversing to the last element//
        }
        temp->next=newnode; //Storing the address of new node in previous node link part//
        
    }

}
void rev(){
    struct node* curr;
    struct node* after;
    struct node*prev;
    curr=head;
    after=head;
    prev=NULL;
    while(after!=NULL){
        after=after->next;
        curr->next=prev;
        prev=curr;
        curr=after;
    }
    head=prev;
}



void print(){
    struct node* temp=head;
    while(temp!=NULL){
        if(temp->next==NULL)
        printf("%d",temp->data);
        else
        printf("%d->",temp->data);
        temp=temp->next;
    }
    printf("\n");
}
int main() {
    
    insertion(1);
    insertion(2);
    insertion(3);
    insertion(4);
    
    print();
    rev();
    print();
  // your code goes here
  return 0;
}

 

     

EXPLANATION: