Address Calculation sort.c

#include<stdio.h>
#include<stdlib.h>
#define MAX 20

struct  node
{
    int info ;
    struct node *link;
};
struct node *head[10];
int n,i,arr[MAX];
void insert(int num,int addr)
{
    struct node *q,*temp;
    temp=  (struct node *) malloc(sizeof(struct node));
    temp->info=num;
    if(head[addr] == NULL || num < head[addr]->info)
    {
        temp->link=head[addr];
        head[addr]=temp;
        return;
    }
    else
    {
        q=head[addr];
        while(q->link != NULL && q->link->info < num)
            q=q->link;
        temp->link=q->link;
        q->link=temp;
    }
}
int large_dig()
{
    int large = 0,ndig = 0 ;
    for(i=0; i<n; i++)
    {
        if(arr[i] > large)
            large = arr[i];
    }
    printf("\nLargest Element is %d , ",large);
    while(large != 0)
    {
        ndig++;
        large = large/10 ;
    }
    printf("Number of digits in it are %d\n\n",ndig);
    return(ndig);
}
int hash_fn(int number,int k)
{
    int digit,addr,i;
    for(i = 1 ; i <=k ; i++)
    {
        digit = number % 10 ;
        number = number /10 ;
    }
    addr=digit;
    return(addr);
}
void addr_sort()
{
    int i,k,dig;
    struct node *p;
    int addr;
    k=large_dig();
    for(i=0; i<=9; i++)
        head[i]=NULL;
    for(i=0; i<n; i++)
    {
        addr=hash_fn( arr[i],k );
        insert(arr[i],addr);
    }

    for(i=0; i<=9 ; i++)
    {
        printf("head(%d) -> ",i);
        p=head[i];
        while(p!=NULL)
        {
            printf("%d ",p->info);
            p=p->link;
        }
        printf("\n");
    }
    i=0;
    for(k=0; k<=9; k++)
    {
        p=head[k];
        while(p!=NULL)
        {
            arr[i++]=p->info;
            p=p->link;
        }
    }
}
int main()
{
    int i;
    printf("Enter the number of elements in the list : ");
    scanf("%d", &n);
    for(i=0; i<n; i++)
    {
        printf("Enter element %d : ",i+1);
        scanf("%d",&arr[i]);
    }
    printf("\nUnsorted list is :\n");
    for(i=0; i<n; i++)
        printf("%d  ",arr[i]);
    printf("\n");
    addr_sort();
    printf("\nSorted list is :\n");
    for(i=0; i<n; i++)
        printf("%d  ",arr[i]);
    printf("\n");
}