In-place reversal of linked list

reverseBetween.cpp

ListNode *reverseBetween(ListNode *head, int m, int n) {
    ListNode dummy(-1), *pre = &dummy;
    dummy.next = head;
    for (int i = 0; i < m - 1; ++i) pre = pre->next;
    ListNode *cur = pre->next;
    for (int i = m; i < n; ++i) {
        ListNode *t = cur->next;
        cur->next = t->next;
        t->next = pre->next;
        pre->next = t;
    }
    return dummy.next;
}

// Use regular linked list reversal
ListNode* reverseBetween(ListNode* head, int m, int n) {
    ListNode *prev = nullptr, *cur = head;
    for(int i = 1; i < m; i++){
        prev = cur;
        cur = cur->next;
    }
    ListNode *beforeStart = prev, *start = cur;
    for(int i = m; i <= n; i++){ //regular reversal
        ListNode* tmp = cur->next;
        cur->next = prev;
        prev = cur;
        cur = tmp;
    }
    start->next = cur;
    if(m == 1) head = prev;
    else beforeStart->next = prev;
    return head;
}