// https://forum.arduino.cc/t/i-want-to-generate-the-random-number-but-not-duplicate/1031827

#include <KickSort.h>

/*
int myRand(int const low, int const high) {
  static int last = random(low, high);

  int value = random(low, high - 1);
  if (value >= last) {
    value++;
  }
  last = value;

  return value;
}
*/

template <size_t n> int myRand(int const low, int const high) {
  static int lasts[n]{};  // Initialisation is not perfect.
  static size_t index = 0;

  int sortedLasts[n];
  memcpy(sortedLasts, lasts, n * sizeof(int));
  KickSort<int>::quickSort(sortedLasts, n);

  int value = random(low, high - n);
  for (int const& last: sortedLasts) {
    if (value >= last) {
      value++;
    }
  }

  lasts[index] = value;
  index = (index + 1) % n;

  return value;
}


void setup() {
  Serial.begin(9600);

  for (size_t i = 0; i < 20; i++) {
    Serial.println(myRand<2>(0, 4));
  }
}

void loop() {}