unsigned int previousMillis =0;
unsigned int currentMillis =0;
int ledPin[7] ={19,18,5,17,16,4,0};
int counter =5;

void alloff()
{
  for(int i =0;i<7;i++)
  {
    digitalWrite(ledPin[i],LOW);
  }
}
void setup()
 {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  for(int i =0;i<7;i++)
  {
    pinMode(ledPin[i], OUTPUT);
  }

}

void loop() {
  // put your main code here, to run repeatedly:
  currentMillis=millis();
  if(currentMillis-previousMillis>=2000)
  {
    counter--;
    if(counter<=0)
    counter=4;
    switch(counter)
    {
      case 1 :
      alloff();
      Serial.println("case 1 executed...");
      // digitalWrite(ledPin[6], LOW);
      digitalWrite(ledPin[1], HIGH);
      digitalWrite(ledPin[2], HIGH);
    
      break;
      case 2 :
      alloff();
      Serial.println("case 2 executed...");
      digitalWrite(ledPin[0], HIGH);
      digitalWrite(ledPin[1], HIGH);
      digitalWrite(ledPin[3], HIGH);
      digitalWrite(ledPin[4],HIGH);
      digitalWrite(ledPin[6], HIGH);
      break;
      case 3 :
      alloff();
      Serial.println("case 3 executed....");
      digitalWrite(ledPin[0], HIGH);
      digitalWrite(ledPin[1], HIGH);
      digitalWrite(ledPin[2], HIGH);
      digitalWrite(ledPin[3], HIGH);
      digitalWrite(ledPin[6], HIGH);
      break;
      case 4 :
      alloff();
      Serial.println("case 4 executed....");
      digitalWrite(ledPin[1], HIGH);
      digitalWrite(ledPin[2], HIGH);
      digitalWrite(ledPin[5], HIGH);
      digitalWrite(ledPin[6], HIGH);
      break;
    }
    previousMillis=currentMillis;
    
  }
}