int trig = 10;
int echo = 9;
int time;
int distance;
int yellow_LED = 5;
int green_LED = 4;
int red_LED = 3;

void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  Serial.begin(9600);
  // put your setup code here, to run once:

}

void loop() {
  // setting the trigger to low state
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  //setting up the trigger pin to high state
  digitalWrite(trig , HIGH);
  delayMicroseconds(10);
  // make the trigger point to low state
  digitalWrite(trig, LOW);

  time = pulseIn(echo,HIGH);
  Serial.print("time = ");
  Serial.println(time);
  distance = time* 0.034/2;
  Serial.print("distance of the object = ");
  Serial.print(distance);
  Serial.println(" cm");
  if (distance <= 100)
  {
    digitalWrite(yellow_LED, HIGH);
    Serial.println("yellow LED is in ON state");
  }
  else
  {
    digitalWrite(yellow_LED, LOW);
  }
  if (distance > 100 && distance <= 200)
  {
    digitalWrite(green_LED, HIGH);
    Serial.println("green LED is in ON state");

  }
  else
  {
    digitalWrite(green_LED, LOW);
  }
  if (distance > 200)
  {
    digitalWrite(red_LED, HIGH);
    Serial.println("red LED is in ON state");

  }
  else
  {
    digitalWrite(red_LED, LOW);
  }

  // put your main code here, to run repeatedly:

}