const auto usage= R"QQ(Shuffle and deal randomizes an array, deals it out one element as a time, then reshuffles.  Repeately pressing the button will show the sequences. Since the randomness is more constrained as the sequence drains, you can guess the last numbers better)QQ";

int questionNumberArray[] = {0, 1, 2, 3, 4, };//5, 6, 7, 8, 9};
const int questionCount = sizeof questionNumberArray / sizeof questionNumberArray[0];
const int button = A0;
int last_button;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println(usage);
  pinMode(button, INPUT_PULLUP);
  // initialise  user-based entropy:
  last_button = digitalRead(button);
  Serial.print("press button when ready...");
  while(digitalRead(button) == last_button){delay(10);}
  while(digitalRead(button) == !last_button){delay(10);}
  randomSeed(random()+micros()); 
  shuffle();
  Serial.println("Go!");
}

void loop() {
  // put your main code here, to run repeatedly:
  static int count = 0;
  static int last_button = digitalRead(button);
  int nowButton = digitalRead(button);
  if (nowButton != last_button) {
    last_button=nowButton;
    if (nowButton == 0) {
      Serial.print(questionNumberArray[count]);
      Serial.print(" ");
      ++count;
      if (count >= questionCount) {
        count = 0;
        shuffle();
        Serial.println();
//        delay(1);
      }
    }
    delay(5);
  }
}

void shuffle() {
  // incorporate more user-based entropy
  randomSeed(random()+micros());
  for (int i = 0; i < questionCount; i++) {
    int n = random(0, questionCount);  // Integer from 0 to questionCount-1
    int temp = questionNumberArray[n];
    questionNumberArray[n] =  questionNumberArray[i];
    questionNumberArray[i] = temp;
  }
}