int ledPins[] = {3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
int totalPins = 10;
//int totalPins = sizeof(ledPins) / sizeof(int);

void setup() {
  for (int i = 0; i < totalPins; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
 for (int j = 0; j < totalPins; j++) {
    digitalWrite(ledPins[j], HIGH);
    delay(500);
  } 
 for (int j = totalPins-1; j >= 0; j--) {
    digitalWrite(ledPins[j], LOW);
    delay(500);
 }
}









/*  Blink random led
int ledPins[] = {3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
int totalPins = sizeof(ledPins) / sizeof(int);
// 1 second delay
int delayTime = 1000;

void setup() {
  // configure the LED pins to behave as OUTPUT mode to send HIGH or LOW signals
  for (int i = 0; i < totalPins; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  blinkRandomLED();
}
void blinkAllLeds() {
  for (int i = 0; i < totalPins; i++) {
    // turn on the LED
    digitalWrite(ledPins[i], HIGH);
  }
  // wait for 1 second
  delay(delayTime);
  for (int i = 0; i < totalPins; i++) {
    // turn off the LED
    digitalWrite(ledPins[i], LOW);
  }
  // wait for one second
  delay(delayTime);
}
void blinkOneLEDAtATime() {
  for (int i = 0; i < totalPins; i++) {
    // turn on the LED
    digitalWrite(ledPins[i], HIGH);
    // wait for 1 second
    delay(delayTime);
    // turn off the LED
    digitalWrite(ledPins[i], LOW);
    // wait for one second
    delay(delayTime);
  }
}
void blinkRandomLED() {
  // select random pin number
  int randomIndex = random(totalPins);
  int pinSelected = ledPins[randomIndex];
  
  // turn on the LED
  digitalWrite(pinSelected, HIGH);
  // wait for 1 second
  delay(delayTime);
  // turn off the LED
  digitalWrite(pinSelected, LOW);
  // wait for one second
  delay(delayTime);
}

*/