Arduino Combination Lock

#include <Servo.h>

Servo lockServo;

const int button1 = 2;
const int button2 = 3;
const int button3 = 4;
const int button4 = 5;
const int greenLED = 12;
const int redLED = 13;

const int correctCombo[] = {1, 3, 2, 4};
int currentCombo[4];
int comboIndex = 0;

boolean locked = true;

void setup() {
  pinMode(button1, INPUT_PULLUP);
  pinMode(button2, INPUT_PULLUP);
  pinMode(button3, INPUT_PULLUP);
  pinMode(button4, INPUT_PULLUP);
  pinMode(greenLED, OUTPUT);
  pinMode(redLED, OUTPUT);
  
  lockServo.attach(9);
  lockServo.write(0);
  
  digitalWrite(redLED, HIGH);
  digitalWrite(greenLED, LOW);
  
  Serial.begin(9600);
  Serial.println("Combination Lock Ready");
}

void loop() {
  if (digitalRead(button1) == LOW) {
    addToCombo(1);
    delay(300);
  }
  if (digitalRead(button2) == LOW) {
    addToCombo(2);
    delay(300);
  }
  if (digitalRead(button3) == LOW) {
    addToCombo(3);
    delay(300);
  }
  if (digitalRead(button4) == LOW) {
    addToCombo(4);
    delay(300);
  }
}

void addToCombo(int button) {
  currentCombo[comboIndex] = button;
  comboIndex++;
  
  Serial.print("Button pressed: ");
  Serial.println(button);
  
  if (comboIndex >= 4) {
    checkCombo();
    comboIndex = 0;
  }
}

void checkCombo() {
  boolean match = true;
  
  for (int i = 0; i < 4; i++) {
    if (currentCombo[i] != correctCombo[i]) {
      match = false;
      break;
    }
  }
  
  if (match) {
    unlock();
  } else {
    Serial.println("Wrong combination!");
    blinkRed();
  }
}

void unlock() {
  Serial.println("Correct! Unlocking...");
  lockServo.write(90);
  digitalWrite(redLED, LOW);
  digitalWrite(greenLED, HIGH);
  delay(3000);
  lock();
}

void lock() {
  Serial.println("Locking...");
  lockServo.write(0);
  digitalWrite(greenLED, LOW);
  digitalWrite(redLED, HIGH);
}

void blinkRed() {
  for (int i = 0; i < 3; i++) {
    digitalWrite(redLED, LOW);
    delay(100);
    digitalWrite(redLED, HIGH);
    delay(100);
  }
}

Change correctCombo array to set your own combination (e.g., {2, 4, 1, 3}).