I'm trying to reverse this linked-list but after giving input it gives output Segmentation fault (core dumped) while printing the list. This only happened when I declare 4th pointer before that it was working fine when there were only three pointers head, newcode, temp.

#include <stdio.h>
#include <stdlib.h>

int main()
    {
        struct node
        {
            int data;
            struct node *next;
        };

    struct node *head, *newnode, *temp;
    int choice = 1;

    // Creating a linked-list
    while (choice)
    {
        newnode = (struct node *)malloc(sizeof(struct node));
        printf("Enter the data: ");
        scanf("%d", &newnode->data);
        newnode->next = 0;
        if (head == 0)
        {
            head = temp = newnode;
        }
        else
        {
            temp->next = newnode;
            temp = newnode;
        }
        printf("Do you want to continue: ");
        scanf("%d", &choice);
    }
    temp = head;

    // Reversing the LL
    struct node *prevnode, *currentnode, *nextnode;
    prevnode = 0;
    currentnode = nextnode = head;
    while (nextnode != 0)
    {
        nextnode = nextnode->next;
        currentnode->next = prevnode;
        prevnode = currentnode;
        currentnode = nextnode;
    }
    head = prevnode;

    // Printing the Linked-list
    while (prevnode != 0)
    {
        printf("%d ", prevnode->data);
        prevnode = prevnode->next;
    }
    return 0;
}

I understand segmentation fault error still can't figure which part is actually causing the error.

CodePudding user response：

You need to initialize head to 0. Pointers are not initialized by default. Otherwise, it works fine.

CodePudding user response：

head is uninitialized, because pointer aren't initialized by default