need help getting the correct output when i run my code im not getting any values printed, im just getting lines of space, im supposed to get the output shown below and need help getting it.

bigint_dllist.c

#include "bigint_dllist.h"

#include

#include

#include

NODE *new_node(char data) {

NODE *np = (NODE*) malloc(sizeof(NODE));

if (np == NULL) {

printf("malloc fails");

return NULL;

}

np->data = data;

np->prev = NULL;

np->next = NULL;

return np;

}

void display_forward(NODE *np) {

if (np == NULL)

return;

NODE *ptr = np;

while (ptr != NULL) {

printf("%d", ptr->data);

ptr = ptr->next;

}

}

void display_backward(NODE *np) {

if (np == NULL)

return;

NODE *ptr = np;

while (ptr != NULL) {

printf("%d ", ptr->data);

ptr = ptr->prev;

}

}

void insert_start(NODE **startp, NODE **endp, NODE *new_np) {

if (*startp == NULL)

return;

NODE *temp = *startp;

new_np->next = temp;

temp->prev = new_np;

*startp = new_np;

}

void insert_end(NODE **startp, NODE **endp, NODE *new_np) {

if (*startp == NULL)

return;

NODE *temp = *endp;

temp->next = new_np;

new_np->prev = temp;

*endp = new_np;

}

void delete_start(NODE **startp, NODE **endp) {

if (*startp == NULL)

return;

NODE *temp = *startp;

temp = temp->next;

(*startp)->next = NULL;

temp->prev = NULL;

free(*startp);

(*startp) = temp;

}

void delete_end(NODE **startp, NODE **endp) {

if (*startp == NULL)

return;

NODE *temp = *endp;

temp = temp->prev;

(*endp)->prev = NULL;

temp->next = NULL;

free(*endp);

*endp = temp;

}

void clean(NODE **startp, NODE **endp) {

if (*startp == NULL)

return;

NODE *temp = *startp;

while (temp != NULL) {

NODE *prev = temp;

temp = temp->next;

if (temp)

temp->prev = NULL;

prev->next = NULL;

free(prev);

}

*startp = NULL;

*endp = NULL;

}

main.c

#include "bigint_dllist.h"

#include

#include

int main(int argc, char* args[]) {

NODE *start = NULL, *end = NULL;

int i=0;

for (i = 0; i<10; i++) {

insert_start(&start, &end, new_node('0'+i));

}

display_forward(start);

printf(" ");

display_backward(end);

delete_start(&start, &end);

delete_end(&start, &end);

printf(" ");

display_forward(start);

clean(&start, &end);

for (i = 0; i<10; i++) {

insert_end(&start, &end, new_node('a'+i));

}

printf(" ");

display_forward(start);

clean(&start, &end);

return 0;

}

bigint_dllist.h

#ifndef DLLIST

#define DLLIST

#include

#include

typedef struct node {

char data;

struct node *prev;

struct node *next;

} NODE;

NODE *new_node(char data);

void display_forward(NODE *start);

void display_backward(NODE *end);

void insert_start(NODE **startp, NODE **endp, NODE *new_np);

void insert_end(NODE **startp, NODE **endp, NODE *new_np);

void delete_start(NODE **startp, NODE **endp);

void delete_end(NODE **startp, NODE **endp);

void clean(NODE **startp, NODE **endp);

#endif

required output

9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1 a b c d e f g h i j