lab 6- 1 แบบกลับ

//main.c
#include<stdio.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;
  int d;
  head = NULL;
  printf("Enter: ");
  do{
    scanf("%d", &d);
    if(d > 0){
      insert_at_front(&head,d);
    }
  }while(d > 0);

  printf("");
  print(head);
  printf("\nSUM=%d", sum(head));

  return 0;
}
void insert_at_front(LN **hptr, int d){

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

void print(LN *head){
    if(head !=NULL){
        if(head->next==NULL){
            printf("in if\n");
            printf("=%d\n",head->data);
        }
        else{
            printf("fisrt in else \n");
            print(head->next);
            printf("Second in else\n");
            printf("=%d\n",head->data);

        }
    }
}

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