Reverse algorithm for a linked list in C

Question

I am trying to reverse a linked list in c, that I created by copying the data from a structure.

I have created the following function named reverselist, after reading a lot of suggestions about reversing a list, but after applying it, and trying again to print I get nothing printed on my screen.

I don't want to just print the file, but I want the linked list permanently changed. Can someone spot out what is the problem in my code?

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

int i,j,temp;

typedef struct{
    int nr;
}PASSENGERS;

typedef struct list1{
    int nr;
    struct list1 *next;
}LIST1;


LIST1* reverselist (LIST1 *head)
{
    LIST1 *cursor=NULL;
    LIST1 *next;
    while(head){
        next=head->next;
        head->next=cursor;
        cursor=head;
        head=next;
    }
    return cursor;
}

int main()
{
    PASSENGERS passenger[53];
    for (j=0;j<53;j++)
        passenger[j].nr=j+1;

    PASSENGERS *start=NULL;
    char selection;
    do{
        printf("0. Exit and Print File\n");
        scanf(" %c",&selection);
    } while (selection!='0');

    LIST1 *list1, *start=NULL;
    for (i=0;i<53;i++){
        list1 = (LIST1 *) malloc (sizeof(LIST1));
        list1->next = NULL;
        list1->nr = passenger[i].nr;

        if (start ==NULL)
            start = list1;
        else //add new node at the beginning of list
        {
            list1->next = start;
            start = list1;
        }
    }

    LIST1 *current = list1;
    printf("The original list is:");
    while (current !=NULL) /* Printing the names on the list ok*/
    {
        printf("%d\n",current->nr);
        current = current->next;
    }

    LIST1* head = NULL;
    head=reverselist(head);

    printf("The reversed list is:");

    while (current !=NULL){
        printf("%d\n",current->nr);
        current = current->next;
    }
}

There are numerous questions about how to reverse the items in a singly-linked list. Are you sure you can't find any of them. — Jonathan Leffler
– Jonathan Leffler, Commented Dec 21, 2016 at 20:25
Well I have found many ways, and I tried to apply some of them.. The one that looks closest to a solution I think is the one I posted here, but still can't seem to make it work.. Thanks for the suggestion, and I am still focused on reading here and there to find the solution ! ! — baskon1
– baskon1, Commented Dec 21, 2016 at 20:27

user21926 · Accepted Answer · 2016-12-21 20:27:14Z

1

This code is obviously wrong, because you're passing NULL to reverselist:

LIST1* head = NULL;
head=reverselist(head);

I'm guessing that this should be:

current = reverselist(list1);

(You don't need the head variable here because you are never using it)

answered Dec 21, 2016 at 20:27

user21926

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3 Comments

baskon1 Over a year ago

Thank you so much, it was just in front of my eyes but couldn't spot the problem!

user21926 Over a year ago

@baskon1 - of the 16 questions you've asked so far on StackOverflow, you've only accepted 1 answer. While you are not required to accept an answer, you should make an effort to when an answer resolves the issues you are facing.

baskon1 Over a year ago

Sorry! Will do it from now on! Thanks!

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