I am not used to code in c and not good at it. I looked at Allen book, the art of md simulation and many other books but, I can’t fix it. I’m so sorry if this looks so dumb and obvious but I’m desperate because it has been months.

This is the code that should update cell_list using the coordinates of each particles(I uploaded part of my whole code, if I need to more, please tell me). Also, I will use this cell_list to calculate forces between particles.

I think updating the cell_list is not working properly. Can someone please help me what I can improve in my code?

typedef struct {
    double x;
    double y;
    double z;
} Particle;

typedef struct Node {
    int name;
    Particle particle;
    struct Node* next;
} Node;

Node* cell_list[NUM_CELL][NUM_CELL][NUM_CELL] = {NULL};

void  modify_cell(int name, double Coord[NBEDS][NDIMS]) {

    double x = Coord[name][0];
    double y = Coord[name][1];
    double z = Coord[name][2];

    int cell_x = (int)(x / CELL_SIZE);
    int cell_y = (int)(y / CELL_SIZE);
    int cell_z = (int)(z / CELL_SIZE);

    if (cell_x >= 0 && cell_x < NUM_CELL && cell_y >= 0 && cell_y < NUM_CELL && cell_z >= 0 && cell_z < NUM_CELL) {

        if (cell_list[cell_x][cell_y][cell_z] != NULL) {
            Node* current = cell_list[cell_x][cell_y][cell_z];
            while (current != NULL) {
                if (current->name == name) {
                   return;
                }
                current = current->next;
            }
        }

        Node* current = cell_list[cell_x][cell_y][cell_z];
        Node* prev = NULL;
        while (current != NULL) {
            if (current->name == name) {
                if (prev != NULL) {
                    prev->next = current->next;
                } else {
                    cell_list[cell_x][cell_y][cell_z] = current->next;
                }
                free(current);
                break;
            }
            prev = current;
            current = current->next;
        }

        Particle new_particle;
        new_particle.x = x;
        new_particle.y = y;
        new_particle.z = z;

        Node* new_node = (Node*)malloc(sizeof(Node));
        if (new_node == NULL) {
            printf("Memory allocation failedn");
            return;
        }
        new_node->name = name;
        new_node->particle = new_particle;
        new_node->next = cell_list[cell_x][cell_y][cell_z];
        cell_list[cell_x][cell_y][cell_z] = new_node;

    } else {
        printf("Particle coordinates out of range.n");
    }
}

I tried to debug and correct this modify_cell() function, however, none of it worked well. This is my latest version of my code. Any help will be useful to me.