CODEWITHSUNDEEP
cpointersdata-structureslinked-listsingly-linked-list
Eshan Pandey
Eshan Pandey

Reputation: 55

Linked list implementation in c, run time error

There is no error when I compile the code, but the program crashes at runtime after two inputs. Maybe there is some logical error that I can not make out. I'm trying to insert nodes at the tail of linked lists while only maintaining head position.

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

struct Node{

    int data;
    struct Node* next;
};

struct Node *head;

//print the element of the lists
void print(){
    printf("\nThe list from head to tail is as follows \n");
    struct Node* temp = head;
    while(temp!=NULL){
        printf("\n %d ",(*temp).data);
        temp = (*temp).next;
    }
}

//insert a node at the tail of the linked list
void insert_at_tail(int data){
    struct Node* temp = head;
    struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
    new_node->data=data;
    new_node->next=NULL;

    if(temp==NULL){
        head=new_node;
    }
    else{
        while(temp!=NULL){temp=temp->next;}
        (*temp).next=new_node;
    }
}
int main(){

    head = NULL;
    int i,data;
    for(i=0;i<5;i++){
        scanf("%d",&data);
        insert_at_tail(data);
    }
    print();

    return 0;
}

Upvotes: 1

Views: 184

Answers (1)

gsamaras
gsamaras

Reputation: 73366

Maybe there is some logical error?

Yes!

Here:

while(temp!=NULL) { temp=temp->next; }
(*temp).next=new_node;

you will loop until temp is actually NULL and then request its next member, so you are asking for next of NULL, thus you are asking for trouble (the program crashes)!

Try doing this instead:

while(temp->next != NULL) { temp=temp->next; }

where you are looping until temp points to the last node of your list. With that change your code should work fine.

PS: Do I cast the result of malloc? No!

Upvotes: 5

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