c 语言输入链表数据（以数字-1作为输入结束的标志），例如建立链表1 2 3 则需输入1 2 3 -1;

可以使用如下代码实现：

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

struct ListNode {
    int val;
    struct ListNode *next;
};

struct ListNode* createList() {
    struct ListNode *head = NULL, *tail = NULL;
    int num;
    while (scanf("%d", &num) == 1 && num != -1) {
        struct ListNode *node = (struct ListNode*)malloc(sizeof(struct ListNode));
        node->val = num;
        node->next = NULL;
        if (head == NULL) {
            head = tail = node;
        } else {
            tail->next = node;
            tail = node;
        }
    }
    return head;
}

int main() {
    struct ListNode *head = createList();
    // do something with the linked list
    return 0;
}