根据输入的数据建立链表，并输出该链表中倒数第二个结点的数据 C语言代码实现

以下是实现该功能的C语言代码：

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

struct Node {
    int data;
    struct Node* next;
};

struct Node* createLinkedList(int n) {
    struct Node* head = NULL;
    struct Node* tail = NULL;
    int data;

    for (int i = 0; i < n; i++) {
        printf("Enter node data: ");
        scanf("%d", &data);

        struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
        newNode->data = data;
        newNode->next = NULL;

        if (head == NULL) {
            head = newNode;
            tail = newNode;
        } else {
            tail->next = newNode;
            tail = newNode;
        }
    }

    return head;
}

int getNthFromEnd(struct Node* head, int n) {
    struct Node* temp = head;
    int length = 0;

    while (temp != NULL) {
        length++;
        temp = temp->next;
    }

    if (n > length) {
        printf("Error: n is greater than the length of the list.");
        return -1;
    }

    int nthFromStart = length - n + 1;
    temp = head;
    for (int i = 1; i < nthFromStart; i++) {
        temp = temp->next;
    }

    return temp->data;
}

int main() {
    int n, secondLast;

    printf("Enter the number of nodes: ");
    scanf("%d", &n);

    struct Node* head = createLinkedList(n);

    secondLast = getNthFromEnd(head, 2);

    printf("Data of second last node: %d", secondLast);

    return 0;
}

该代码中包含了两个函数：

- `createLinkedList`：该函数会根据输入的数据创建一个链表，并返回链表的头指针。
- `getNthFromEnd`：该函数会返回链表中倒数第n个节点的数据。

在 `main` 函数中，先调用 `createLinkedList` 创建链表，然后调用 `getNthFromEnd` 函数获取倒数第二个节点的数据，并输出到控制台上。