数据结构中线性表在不知道长度的时候怎么输入数据(语言-c语言)

我用循环输入没有输出，刚刚开始学，希望可以解答一下，求指教😊😊非常感谢

#include <string.h>
#include <stdio.h>

typedef struct _node
{
    char *data;
    int length;
} Node;

int main()
{
    Node head = {0};
    head.data = (char *)malloc(100 * sizeof(char));
    int i = 0;
    char ch;
    while (i < 100 && (ch = getchar()) != '\n')
    {
        if (ch == ' ')
            continue;
        head.data[i++] = ch;
    }
    head.length = i;

    for (i = 0; i < head.length - 1; i++)
    {
        for (int j = i + 1; j < head.length; j++)
        {
            if (head.data[i] == head.data[j])
            {
                memcpy(&head.data[j], &head.data[j + 1], head.length - j);
                head.length--;
                i--;
            }
        }
    }
    char *p = (char *)malloc(head.length * sizeof(char));
    memcpy(p, head.data, head.length);
    free(head.data);
    head.data = p;

    for (i = 0; i < head.length; i++)
    {
        printf("%c ", head.data[i]);
    }

    return 0;
}

供参考：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
typedef int DataType;
typedef struct node {
    DataType data;
    struct node* link;
}Node;

//初始化空链表
Node* initLinkList() {
    Node* head = (Node*)malloc(sizeof(Node)); //头节点
    if (head == NULL) {
        printf("链表初始化失败\n");
        return NULL;
    }
    head->link = NULL;
    return head;
}

Node* creatNode(DataType ele) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    if (newNode == NULL) {
        printf("节点创建失败\n");
        return NULL;
    }
    newNode->data = ele;
    newNode->link = NULL;
    return newNode;
}

Node* getTail(Node* L) {//获取尾指针
    Node* pMove = L;
    while (pMove->link) {
        pMove = pMove->link;
    }
    return pMove;
}

void tailInsert(Node* L, DataType ele) {
    if (L == NULL) {
        printf("链表未初始化\n");
        return;
    }
    Node* newNode = creatNode(ele);
    getTail(L)->link = newNode;
}

void deleteDuplicates(Node* L)  //链表去重
{
    if (L == NULL || L->link == NULL)  return;
    Node* p, * pnext, * pnextpre, * tmp;
    p = L;
    while (p->link)
    {
        pnextpre = p->link;
        pnext = pnextpre->link;
        while (pnext) {
            if (p->link->data == pnext->data)
            {
                tmp = pnext;
                pnextpre->link = pnext->link;
                free(tmp);
                pnext = pnextpre->link;
            }
            else{
                pnextpre = pnext;
                pnext = pnext->link;
            }
        }
        p = p->link;
    }
}

void Print(Node* L) {
    Node* p = L->link;
    if (!p) {
        printf("NULL");
    }
    else {
        while (p) {
            printf(p == L->link ? "%d" : " %d", p->data);
            p = p->link;
        }
    }
    printf("\n");
}

int main()
{
    int i;
    srand((unsigned int)time(NULL));
    Node* List = initLinkList();
    for (i = 0; i < 20; i++)
        tailInsert(List, rand() % 10);
    Print(List);

    deleteDuplicates(List);//去重
    Print(List);
    return 0;
}