list.c

typedef struct {
  Element* start;
  size_t len;
  size_t cap;
} vector;

vector* vector_new () {
  vector* vec = (vector*) malloc(sizeof(vec));
  vec->cap = 10;
  vec->start = (Element*) malloc(sizeof(Element) * vec->cap);
  return vec;
}

void vector_push (vector* vec, Element* elem) {
  if (vec->len >= vec->cap) {
    vector_grow(vec);
  }
  vec->start[vec->len++] = elem;
}

void vector_grow (vector* vec) {
  int newCap = vec->cap * 2;
  Element* newStart = (Element*) malloc(sizeof(newStart) * newCap);
  memcpy(newStart, vec->start);
  vec->start = newStart;
  vec->cap = newCap;
}

void vector_free (vector* vec) {
  free(vec->start);
  free(vec);
}

vector matrice[10];

matrice[0] = vector_new();
int i;
for (i = 0; i < random(); i++) {
  vector_push(matrice[0], Element{});
}
matrice[1] = vector_new();
matrice[2] = vector_new();