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