#include <Servo.h>
const int IN1 = 7;
const int IN2 = 6;
const int IN3 = 5;
const int IN4 = 4;
const int trigPin = 10;
const int echoPin = 11;
const int servoPin = 9;

Servo myServo;

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  myServo.attach(servoPin);
  myServo.write(90);
  Serial.begin(9600);
}

void loop() {
  long duration, distance;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  if (distance < 20) {
    stopCar();
    avoidObstacle();
  } else {
    moveForward();
  }

  delay(100);
}
void moveForward() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
}
void stopCar() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
}
void avoidObstacle() {
  myServo.write(45);
  delay(500);
  myServo.write(135);
  delay(500);
  myServo.write(90);
  delay(500);
}