int led_pins[8]={19,18,5,17,16,4,0,2};
void setup() {
  for(int i=0;i<8;i++){
     pinMode(led_pins[i],OUTPUT);
  }
} 
    
void loop() {
  for(int i=0;i<8;i++){
     //all_off();
    digitalWrite(led_pins[i],HIGH);
    delay(1000);
  }
  for(int i=7;i>=0;i--){
     //all_off();
    digitalWrite(led_pins[i],LOW);
    delay(1000);
  }
  }

void all_off(void){
  for(int i=0;i<8;i++){
    digitalWrite(led_pins[i],LOW);
  } 
  }