const int ledCount = 10; // amount of pins we will use. This integer will remain constant
int ledPins[] = {3,4,5,6,7,8,9,10,11,12}; // array of pins
void setup() {
  // setup the program
  for(int i = 0; i < 10; i++){ // go through array and set all the pins to output
      pinMode(ledPins[i], OUTPUT);
    }

}

void loop() {
  // put your main code here, to run repeatedly:
  for(int i = 0; i < ledCount; i++){
    barGraphDisplay(i); // the ith LED of the bar graph will light up
  }
}

// determine which LED will light up
void barGraphDisplay(int ledOn){
  for(int i = 0; i < ledCount; i++){
    if(i == ledOn){
      digitalWrite(ledPins[i], HIGH); // selected pin output HIGH
    } else {
      digitalWrite(ledPins[i], LOW); // other pins output LOW
    }
  }
  delay(100); // delay 100 ms
}