You said: certain amount of numbers; do you know that number upfront? If yes - you can allocate memory for that many values. If not - you'd need to implement some logic to allocate additional storage as needed. For example by doubling the already allocated space. You can increment the capacity by one to avoid wasted space, at the cost of repeated copying of your data.

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

int main()
{
  char ch = 0;
  int size = 0, capacity = 1;
  int* c = malloc(sizeof(int) * capacity);
  while (1) {
    scanf("%d%c", &c[size], &ch);
    if (ch == '\n')
      break;
    size++;
    if (size == capacity)
    {
      capacity *= 2; // use whatever policy to increase the capacity
      c = realloc(c, sizeof(int) * capacity);
    }
  }
  return 0;
}

Read one character at a time (using getc(stdin)) and grow the string (realloc) as you go.

Here's a function I wrote some time ago. Note it's intended only for text input.

char *getln()
{
    char *line = NULL, *tmp = NULL;
    size_t size = 0, index = 0;
    int ch = EOF;

    while (ch) {
        ch = getc(stdin);

        /* Check if we need to stop. */
        if (ch == EOF || ch == '\n')
            ch = 0;

        /* Check if we need to expand. */
        if (size <= index) {
            size += CHUNK;
            tmp = realloc(line, size);
            if (!tmp) {
                free(line);
                line = NULL;
                break;
            }
            line = tmp;
        }

        /* Actually store the thing. */
        line[index++] = ch;
    }

    return line;
}