How to make Obstacle Avoiding Car ?

Obstacle Avoiding Car. An Arduino controlled car that avoids obstacles (ie. walls or objects in front of it).

Circuit diagram

Code

#include //Servo motor library. This is standard library
#include //Ultrasonic sensor function library. You must install this library

//our L298N control pins
const int LeftMotorForward = 7;
const int LeftMotorBackward = 6;
const int RightMotorForward = 4;
const int RightMotorBackward = 5;

//sensor pins
#define trig_pin A1 //analog input 1
#define echo_pin A2 //analog input 2

#define maximum_distance 200
boolean goesForward = false;
int distance = 100;

NewPing sonar(trig_pin, echo_pin, maximum_distance); //sensor function
Servo servo_motor; //our servo name

void setup(){

pinMode(RightMotorForward, OUTPUT);
pinMode(LeftMotorForward, OUTPUT);
pinMode(LeftMotorBackward, OUTPUT);
pinMode(RightMotorBackward, OUTPUT);

servo_motor.attach(10); //our servo pin

servo_motor.write(115);
delay(2000);
distance = readPing();
delay(100);
distance = readPing();
delay(100);
distance = readPing();
delay(100);
distance = readPing();
delay(100);
}

void loop(){

int distanceRight = 0;
int distanceLeft = 0;
delay(50);

if (distance = distanceLeft){
turnRight();
moveStop();
}
else{
turnLeft();
moveStop();
}
}
else{
moveForward();
}
distance = readPing();
}

int lookRight(){
servo_motor.write(50);
delay(500);
int distance = readPing();
delay(100);
servo_motor.write(115);
return distance;
}

int lookLeft(){
servo_motor.write(170);
delay(500);
int distance = readPing();
delay(100);
servo_motor.write(115);
return distance;
delay(100);
}

int readPing(){
delay(70);
int cm = sonar.ping_cm();
if (cm==0){
cm=250;
}
return cm;
}

int speed=225;

void moveStop(){

digitalWrite(RightMotorForward, LOW);
digitalWrite(LeftMotorForward, LOW);
digitalWrite(RightMotorBackward, LOW);
digitalWrite(LeftMotorBackward, LOW);
}

void moveForward(){

if(!goesForward){

goesForward=true;

digitalWrite(LeftMotorForward, HIGH);
digitalWrite(RightMotorForward, HIGH);

digitalWrite(LeftMotorBackward, LOW);
digitalWrite(RightMotorBackward, LOW);
}
}

void moveBackward(){

goesForward=false;

digitalWrite(LeftMotorBackward, HIGH);
digitalWrite(RightMotorBackward, HIGH);

digitalWrite(LeftMotorForward, LOW);
digitalWrite(RightMotorForward, LOW);

}

void turnRight(){

digitalWrite(LeftMotorForward, HIGH);
digitalWrite(RightMotorBackward, HIGH);