// define pins for ultrasonic sensor and LEDs
const int trigPin = 2;
const int echoPin = 3;
const int greenLedPin = 4;
const int redLedPin = 5;
const int trigPin2 = 6;
const int echoPin2 = 7;
const int greenLedPin2 = 8;
const int redLedPin2 = 9;
const int trigPin3 = 10;
const int echoPin3 = 11;
const int greenLedPin3 = 12;
const int redLedPin3 = 13;


// define variables to keep track of LED states and previous distance
bool greenLedOn = false;
bool redLedOn = false;
bool greenLedOn2 = false;
bool redLedOn2 = false;
bool greenLedOn3 = false;
bool redLedOn3 = false;
int prevDistance = 0;
int prevDistance2 = 0;
int prevDistance3 = 0;

void setup() {
  // initialize serial communication
  Serial.begin(9600);
  
  // define pin modes
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(greenLedPin, OUTPUT);
  pinMode(redLedPin, OUTPUT);
  pinMode(trigPin2, OUTPUT);
  pinMode(echoPin2, INPUT);
  pinMode(greenLedPin2, OUTPUT);
  pinMode(redLedPin2, OUTPUT);
}

void loop() {
  // send 10us pulse to trigger pin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // measure the duration of the pulse and calculate distance in cm
  long duration = pulseIn(echoPin, HIGH);
  int distance = duration / 58;
  
  // print distance to serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  
  // check if distance has changed since last measurement
  if (distance != prevDistance && distance != prevDistance + 1 && distance != prevDistance - 1) {
    // turn off both LEDs
    digitalWrite(greenLedPin, LOW);
    digitalWrite(redLedPin, LOW);
    
    // turn on green LED if distance is less than 10cm, else turn on red LED
    if (distance < 10) {
      digitalWrite(greenLedPin, HIGH);
      greenLedOn = true;
    } else {
      digitalWrite(redLedPin, HIGH);
      redLedOn = true;
    }
    
    // wait for 1 second
    delay(1000);
    
    // turn off the LED that was turned on
    if (greenLedOn) {
      digitalWrite(greenLedPin, LOW);
      greenLedOn = false;
    } else {
      digitalWrite(redLedPin, LOW);
      redLedOn = false;
    }
    
    // update previous distance
    prevDistance = distance;
  }
  
  // wait for a moment before taking another measurement
  delay(100);


  // send 10us pulse to trigger pin
  digitalWrite(trigPin2, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin2, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin2, LOW);
  
  // measure the duration of the pulse and calculate distance in cm
  long duration2 = pulseIn(echoPin2, HIGH);
  int distance2 = duration2 / 58;
  
  // print distance to serial monitor
  Serial.print("Distance2: ");
  Serial.print(distance2);
  Serial.println(" cm");
  
  // check if distance has changed since last measurement
  if (distance2 != prevDistance2 && distance2 != prevDistance2 + 1 && distance2 != prevDistance2 - 1) {
    // turn off both LEDs
    digitalWrite(greenLedPin2, LOW);
    digitalWrite(redLedPin2, LOW);
    
    // turn on green LED if distance is less than 10cm, else turn on red LED
    if (distance2 < 10) {
      digitalWrite(greenLedPin2, HIGH);
      greenLedOn2 = true;
    } else {
      digitalWrite(redLedPin2, HIGH);
      redLedOn2 = true;
    }
    
    // wait for 1 second
    delay(1000);
    
    // turn off the LED that was turned on
    if (greenLedOn2) {
      digitalWrite(greenLedPin2, LOW);
      greenLedOn2 = false;
    } else {
      digitalWrite(redLedPin2, LOW);
      redLedOn2 = false;
    }
    
    // update previous distance
    prevDistance2 = distance2;
  }
  
  // wait for a moment before taking another measurement
  delay(100);


// send 10us pulse to trigger pin
  digitalWrite(trigPin3, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin3, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin3, LOW);
  
  // measure the duration of the pulse and calculate distance in cm
  long duration3 = pulseIn(echoPin3, HIGH);
  int distance3 = duration3 / 58;
  
  // print distance to serial monitor
  Serial.print("Distance3: ");
  Serial.print(distance3);
  Serial.println(" cm");
  
  // check if distance has changed since last measurement
  if (distance3 != prevDistance3 && distance3 != prevDistance3 + 1 && distance3 != prevDistance3 - 1) {
    // turn off both LEDs
    digitalWrite(greenLedPin3, LOW);
    digitalWrite(redLedPin3, LOW);
    
    // turn on green LED if distance is less than 10cm, else turn on red LED
    if (distance3 < 10) {
      digitalWrite(greenLedPin3, HIGH);
      greenLedOn3 = true;
    } else {
      digitalWrite(redLedPin3, HIGH);
      redLedOn3 = true;
    }
    
    // wait for 1 second
    delay(1000);
    
    // turn off the LED that was turned on
    if (greenLedOn3) {
      digitalWrite(greenLedPin3, LOW);
      greenLedOn3 = false;
    } else {
      digitalWrite(redLedPin3, LOW);
      redLedOn3 = false;
    }
    
    // update previous distance
    prevDistance3 = distance3;
  }
  
  // wait for a moment before taking another measurement
  delay(100);
}