举栗子：

剑指 Offer II 021. 删除链表的倒数第 n 个结点

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

int n, k;

struct ListNode 
{
    int val;
    ListNode *next;
    ListNode(int x) :val(x), next(nullptr) {}
};

ListNode* create()
{
    auto dummy = new ListNode(-1), cur = dummy;
    for (int i = 0; i < n; i++) {
        int x;
        cin >> x;
        auto p = new ListNode(x);
        cur = cur->next = p;
    }

    auto head = dummy->next;
    delete dummy;
    return head;
}

void print(ListNode *head) 
{
    for (auto p = head; p; p = p->next)
        cout << p->val << ' ';
    cout << endl;
}

ListNode* deleteKthFromEnd(ListNode* head, int k)
{
    auto dummy = new ListNode(-1);
    dummy->next = head;

    auto p = dummy;
    for (int i = 0; i < n - k; i ++ ) p = p->next;
    auto tmp = p->next;
    p->next = p->next->next;
    delete tmp;

    head = dummy->next;
    delete dummy;

    return head;
}

int main()
{
    cin >> n >> k;  //n是链表中结点个数, k是待删除链表中倒数第k个结点

    ListNode* head = create();
    print(head);

    head = deleteKthFromEnd(head, k);

    print(head);
    return 0;
}