odd even random pointer, linked list

I need to modify the SLL random pointers in such a way that ,All odd numbers in the list are connected by random pointers in the same order in which they are in SLL and the same for even numbers. I mean... I need to modify random pointers in such a way that First Odd number in List random will point to second odd number in the list and so on. I return a array [odd_count,even_count]. here is my code...I am getting NullReferenceException. I am not able find out where the pointer is not handled properly in my code...here is my code...

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

struct oddevennode{
    int data;
    struct oddevennode * next;
    struct oddevennode * random;
};

int * oddeven_sll(struct oddevennode *head){
    if (head == NULL) return NULL;
    int final_array[2]; 
    int odd_count = 0; int even_count = 0; 
    oddevennode *front = head; oddevennode *front_odd = head; oddevennode *front_even = head; 
oddevennode *odd_pt_front = front_odd; oddevennode *odd_pt_rear = front_odd;
oddevennode *even_pt_front = front_even; oddevennode *even_pt_rear = front_even;
    while (front != NULL){
        if (front->data % 2 == 0) even_count++;
        else odd_count++;
        front = front->next;
    }
    final_array[0] = odd_count;
    final_array[1] = even_count;
    if (odd_count != 0 && even_count != 0){
       while (front_odd->next != NULL){
           if (front_odd->data % 2 == 0){
               front_odd = front_odd->next;
               odd_pt_front = odd_pt_front->next;
               odd_pt_rear = odd_pt_rear->next;
           }
           else if (front_odd->data % 2 == 1){
               odd_pt_rear = odd_pt_rear->next;
               while (odd_pt_rear->data % 2 == 0){
                   odd_pt_rear = odd_pt_rear->next;
                   if (odd_pt_rear->next == NULL) break;
               }
               odd_pt_front->random = odd_pt_rear;
               odd_pt_front = odd_pt_rear;
               front_odd = odd_pt_rear;
           }
           if (odd_pt_rear->next == NULL) break;
        }
        while (front_even->next != NULL){
           if (front_even->data % 2 == 1){
               front_even = front_even->next;
               even_pt_front = even_pt_front->next;
               even_pt_rear = even_pt_rear->next;
           }
           else if (front_even->data % 2 == 0){
               even_pt_rear = even_pt_rear->next;
               while (even_pt_rear->data % 2 == 1){
                   even_pt_rear = even_pt_rear->next;
                   if (even_pt_rear->next == NULL) break;
               }
               even_pt_front->random = even_pt_rear;
               even_pt_front = even_pt_rear;
               front_even = even_pt_rear;
           }
           if (even_pt_rear->next == NULL) break;
       }
    }
    return final_array;
}

please help me to find my mistake in the above implementation... eg: 10->3->6->5->8->1->3

3->5->1->3 [Odd numbers if traversed through Randoms from 3] 10->6->8 [Even numbers if traversed through Randoms from 10] thanks in advance