#include <LiquidCrystal_I2C.h>  

const int numRows = 4;  
const int numCols = 4;  
const int debounceTime = 20;  
const char keymap[numRows][numCols] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};
const int rowPins[numRows] = {12, 11, 10, 9}; 
const int colPins[numCols] = {7, 6, 5, 4};

LiquidCrystal_I2C lcd(0x27, 16, 2);  

const String password = "123";  
const String password2 = "321"; 
String enter = "";  

void setup()
{
  Serial.begin(9600);
  lcd.begin(16, 2);  
  lcd.backlight(); 

  for (int row = 0; row < numRows; row++)
  {
    pinMode(rowPins[row], INPUT_PULLUP);  
  }

  for (int column = 0; column < numCols; column++)
  {
    pinMode(colPins[column], OUTPUT);  
    digitalWrite(colPins[column], HIGH);  
  }
}


void loop()
{
  
  char key = getKey();
  if (key != 0)  
  {
    
    lcd.print(key);
    
    if (key == '#')
    {
      if (enter == password)
      {
        lcd.clear();
        lcd.setCursor(0, 0);
        digitalWrite(2, HIGH);
      }
      else if (enter == password2)
      {
        lcd.clear();
        lcd.setCursor(0, 0);
        digitalWrite(2,LOW);
      }
      else
      {
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Invalid password");
      }
      enter = "";  
      lcd.clear();
    }
    else
    {
      enter += key;  
    }
    
  }
}


char getKey()
{
  char key = 0;  
  for (int column = 0; column < numCols; column++)
  {
    digitalWrite(colPins[column], LOW);  
    for (int row = 0; row < numRows; row++)  
    {
      if (digitalRead(rowPins[row]) == LOW) 
      {
        delay(debounceTime);  
        while (digitalRead(rowPins[row]) == LOW) ;  
        key = keymap[row][column];  
        digitalWrite(colPins[column], HIGH); 
        return key;  
      }
    }
    digitalWrite(colPins[column], HIGH);  
  }
  return key;  
}