Delete all nodes whose node digit sum is odd from circular linked list in c

C program for Delete all nodes whose node digit sum is odd from circular linked list. Here problem description and other solutions.

// Include header file
#include <stdio.h>
#include <stdlib.h>

// C Program
// Remove all the Odd digit sum nodes from a circular linked list
typedef struct LinkNode
{
    // Define useful field of LinkNode
    int data;
    struct LinkNode * next;
}LinkNode;

LinkNode * getLinkNode(int data)
{
    // Create dynamic memory of LinkNode
    LinkNode * ref = (LinkNode * ) malloc(sizeof(LinkNode));
    if (ref == NULL)
    {
        // Failed to create memory 
        return NULL;
    }
    ref->data = data;
    ref->next = NULL;
    return ref;
}
typedef struct CircularLinkedList
{
    // Define useful field of CircularLinkedList
    struct LinkNode * head;
    struct LinkNode * tail;
}CircularLinkedList;

CircularLinkedList * getCircularLinkedList()
{
    // Create dynamic memory of CircularLinkedList
    CircularLinkedList * ref = 
      (CircularLinkedList * ) malloc(sizeof(CircularLinkedList));
    if (ref == NULL)
    {
        // Failed to create memory 
        return NULL;
    }
    // Set initial value
    ref->head = NULL;
    ref->tail = NULL;
    return ref;
}
//Add node at the end position efficiently
void insert(CircularLinkedList * ref, int value)
{
    // Create a new node
    LinkNode * node = getLinkNode(value);
    if ((ref->head == NULL))
    {
        // When first node
        ref->head = node;
    }
    else
    {
        // Connect new node at the last
        ref->tail->next = node;
    }
    // Connect last node to first node
    node->next = ref->head;
    // Set new last node
    ref->tail = node;
}
// Display node element of circular linked list
void display(CircularLinkedList * ref)
{
    if ((ref->head == NULL))
    {
        printf("\n Empty Linked List");
    }
    else
    {
        // First node of linked list
        printf(" %d ", ref->head->data);
        LinkNode * temp = ref->head->next;
        // Display linked list node
        while (temp != NULL && temp != ref->head)
        {
            // Display node value
            printf(" %d ", temp->data);
            // Visit to next node
            temp = temp->next;
        }
    }
}
// Sum of digits
int digitSum( int num)
{
    int n = num;
    int sum = 0;
    if ((n < 0))
    {
        // When node value is negative
        n = -n;
    }
    while (n > 0)
    {
        sum += (n % 10);
        n = n / 10;
    }
    return sum;
}
void removeOddDigitSumNode(CircularLinkedList * ref)
{
    if ((ref->head == NULL))
    {
        return;
    }
    LinkNode * temp = ref->head;
    LinkNode * auxiliary = ref->head;
    LinkNode * point = NULL;
    while (temp != NULL)
    {
        if (((digitSum(temp->data) % 2) != 0))
        {
            auxiliary = temp;
            temp = temp->next;
            if ((auxiliary == ref->head))
            {
                // Enter to remove first node
                if ((auxiliary == ref->tail))
                {
                    // Enter to removing single node
                    ref->tail = NULL;
                    ref->head = NULL;
                    temp = NULL;
                    point = NULL;
                }
                else
                {
                    ref->head = temp;
                    ref->tail->next = temp;
                }
            }
            else if ((auxiliary == ref->tail))
            {
                // When Remove last node
                if ((point != NULL))
                {
                    point->next = ref->head;
                }
                ref->tail = point;
            }
            else
            {
                // When removing intermediate node
                if ((point != NULL))
                {
                    point->next = temp;
                }
            }
            free(auxiliary);
            auxiliary = NULL;
        }
        else
        {
            point = temp;
            // Visit to next node
            temp = temp->next;
            if ((temp == ref->head))
            {
                // Stop the process
                temp = NULL;
            }
        }
    }
}
int main()
{
    CircularLinkedList * cll = getCircularLinkedList();
    // Insert node
    insert(cll, 131);
    insert(cll, 12);
    insert(cll, 33);
    insert(cll, 10);
    insert(cll, 143);
    insert(cll, 91);
    insert(cll, 27);
    insert(cll, 125);
    insert(cll, 89);
    printf("\n Before remove odd digit sum nodes\n");
    display(cll);
    /*
        Node   Digit Sum    Odd
        ----- -----------  --------
        131   [1+3+1] 5     Yes
        12    [1+2]   3     Yes
        33    [3+3]   6     No
        10    [10]    1     Yes
        143   [1+4+3] 8     No
        91    [9+1]   10    No
        27    [2+7]   9     Yes        
        125   [1+2+5] 8     No
        89    [8+9]   17    Yes
        --------------------------
        Result 
        ------
        33 → 143 → 91 → 125 ┐ 
         └-----------------⤶
            
    */
    removeOddDigitSumNode(cll);
    printf("\n After remove odd digit sum nodes\n");
    display(cll);
}

Output

 Before remove odd digit sum nodes
 131  12  33  10  143  91  27  125  89
 After remove odd digit sum nodes
 33  143  91  125