Sorting a linked list with 0s 1s and 2s

// Sorts a list containing 0, 1, and 2 (without moving the node)
Node* sortList012(Node *head) {
    // Start and end of list of zeros
    Node *_0st = NULL, *_0end = NULL;
    // Start and end of list of ones
    Node *_1st = NULL, *_1end = NULL;
    // Start and end of list of twos
    Node *_2st = NULL, *_2end = NULL;

    Node *ptr = head;
    while(ptr)
    {
        Node *next = ptr->next;
        switch(ptr->data)
        {
            case 0:
                if(!_0st)       // first zero to come
                {
                    _0st = ptr;
                }
                else
                {
                    _0end->next = ptr;
                }
                _0end = ptr;
                if(_1st) _0end->next = _1st;            // link it the start of 1  ie 0 .... 0 -> 1 ....
                if(!_1st && _2st) _0end->next = _2st;   // if there is no 1 but 2  ie 0 .... 0 -> 2 ....
                break;
            case 1:
                if(!_1st)       // first one to come
                {
                    _1st = ptr;
                    if(_0end) _0end->next = _1st;       // link it to the end of 0s
                }
                else
                {
                    _1end->next = ptr;
                }
                _1end = ptr;
                _1end->next = _2st;
                break;
            case 2:
                if(!_2st)
                {
                    _2st = ptr;
                    if(_1end) _1end->next = _2st;           // link it to the end of 1s  ie 0 .... 0 -> 1 ....
                    else if(_0end) _0end->next = _2st;      // if there is no 1 but 0   ie 0 .... 0 -> 2 ....
                }
                else
                {
                    _2end->next = ptr;
                }
                _2end = ptr;
                _2end->next = NULL;
                break;
        }
        ptr = next;
    }
    // start of zeros is the start of the linked list
    return _0st;
}