// C++ code
//

int led[5]={10,9,8,7,6} ;

void setup()
{
  for(int i=0;i<=4;i++){
    pinMode(led[i],OUTPUT);
  } 
}

void loop()
{
  for(int i=0;i<=4;i++){
    digitalWrite(led[i],HIGH);
    delay(500);
    digitalWrite(led[i],LOW);
    delay(500);
  }
  for(int i=3;i>=1;i--){
    digitalWrite(led[i],HIGH);
    delay(500);
    digitalWrite(led[i],LOW);
    delay(500);
  }
}

Source : Youtube Life Tech