int pinLED[] = {2,3,4,5,6,7};

void setup() {
  // put your setup code here, to run once:
  for (int i = 0; i < 6; i++) {
    pinMode(pinLED[i], OUTPUT);
  }

}

void loop() {
  // put your main code here, to run repeatedly:

  // 从左往右
  for (int i = 0; i < 6; i++) {
    digitalWrite(pinLED[i], HIGH);
    delay(1000);
    digitalWrite(pinLED[i], LOW);
  }
  // 从右往左
  for (int i = 5; i >= 0; i--) {
    digitalWrite(pinLED[i], HIGH);
    delay(1000);
    digitalWrite(pinLED[i], LOW);
  }
}