set.c

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

struct number_set {
  int *arr;
  size_t len;
  size_t cap;
};
void set_init(struct number_set *set) {
  set->cap = 16;
  set->len = 0;

  set->arr = (int*)malloc(sizeof(*set->arr) * set->cap);
}
void set_add(struct number_set *set, int n) {
  for (size_t i = 0; i < set->len; ++i) {
    if (set->arr[i] == n) return;
  }

  if (set->cap == set->len) {
    set->cap *= 2;
    set->arr = (int*)realloc(set->arr, sizeof(*set->arr) * set->cap);
  }

  set->arr[set->len++] = n;
}
void set_sort(struct number_set *set) {
  int tmp;
  for (size_t i = 0; i < set->len-1; ++i) {
    for (size_t j = 0; j < set->len - 1 - i; ++j) {
      if (set->arr[j] > set->arr[j+1]) {
        tmp = set->arr[j];
        set->arr[j] = set->arr[j+1];
        set->arr[j+1] = tmp;
      }
    }
  }
}

int main() {
  int n;
  struct number_set set;
  set_init(&set);

  puts("Please enter the numbers you like. cntl+D to finish");

  for (;;) {
    fputs("> ", stdout);
    scanf("%d", &n);

    if (feof(stdin)) {
      putchar('\n');
      break;
    }

    set_add(&set, n);
  }

  set_sort(&set);

  fputs("You like the following numbers:", stdout);

  for (size_t i = 0; i < set.len; ++i) {
    printf(" %d", set.arr[i]);
  }

  putchar('\n');
}