change Insert At Front linked list to Insert At Back linked list in C Language

Question

hello , to day i'm want to change Insert At Front linked list to Insert At Back linked list,i'm not sure Insert At Back code but Insert At Front code not have bug .

problem list is function void insert_at_back(LN **hptr, int d) in code second.

how to from : C program to insert node at the end of Singly Linked List

this is Insert At Front linked list code (NOT have bug)

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

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

    typedef struct listnode LN;

    void insert_at_front(LN **hptr, int d);
    void print(LN *head);
    int sum(LN *head);

    int main(){
      LN *head;
      head = NULL;
      int d;
      printf("Enter data: ");
      do{
        scanf("%d", &d);
        if(d > 0){
            insert_at_front(&head,d);
        }
      }while(d > 0);
        printf("=");
        print(head);
        printf("\n=%d", sum(head));
      return 0;
    }

    void insert_at_front(LN **hptr, int d){

        LN* newNode= (LN*)malloc(sizeof(LN));
        newNode->data = d;
        newNode->next= *hptr;
        *hptr = newNode;
    }

    void print(LN *head){
        while(head !=NULL){
            printf("%d ",head->data);
            head = head->next;
        }
    }

    int sum(LN *head){
        int temp=0;
        while(head !=NULL){
            temp+=head->data;
            head = head->next;
        }
        return temp;
    }

This is Insert At Back linked list code (it have problem or bug)

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

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

typedef struct listnode LN;

void insert_at_back(LN **hptr, int d);
void print(LN *head);
int sum(LN *head);

int main(){
  LN *head;
  head = NULL;
  int d;
  printf("Enter data: ");
  do{
    scanf("%d", &d);
    if(d > 0){
        insert_at_back(&head,d);
    }
  }while(d > 0);
    printf("=");
    print(head);
    printf("\n=%d", sum(head));
  return 0;
}

void insert_at_back(LN **hptr, int d){
    LN* head = *hptr;
    LN* newNode = (LN*)malloc(sizeof(LN));
    if(newNode==NULL){
        printf("Unable to allocate memory\n");
    }else{
        newNode->data = d;
        newNode->next= NULL;
        while(head->data!= NULL){
            head=head->next;
        }
        head->next=newNode;
    }
}

void print(LN *head){
    while(head !=NULL){
        printf("%d ",head->data);
        head = head->next;
    }
}

int sum(LN *head){
    int temp=0;
    while(head !=NULL){
        temp+=head->data;
        head = head->next;
    }
    return temp;
}

Thank you for answer ,i'm sorry if u not understand.

i'm newbie

ihm

change while(head->data!= NULL) to while(head->next !=NULL) and try — Varun, Oct 31 '17 at 12:32

score 0 · Accepted Answer · answered Oct 31 '17 at 12:41

There are few of problems in your insert_at_back() function.

First problem:

while(head->data!= NULL){

This should be :

while(head->next!= NULL){

Second problem:

Not checking for head pointer NULL in insert_at_back() function.

Third problem:

Not initializing the hptr in insert_at_back() function.

Your insert_at_back() should be:

void insert_at_back(LN **hptr, int d){
    LN* head = *hptr;
    LN* newNode = malloc(sizeof(LN));
    if(newNode==NULL){
        printf("Unable to allocate memory\n");
    }else{
        newNode->data = d;
        newNode->next= NULL;
        if (head != NULL) {
            while(head->next!= NULL){
                head=head->next;
            }
            head->next=newNode;
        }
        else
            *hptr = newNode;
   }
}

Last but not least - do not typecast malloc result.

change Insert At Front linked list to Insert At Back linked list in C Language

1 Answers1