#include <LiquidCrystal.h>
#include <Keypad.h>
#include <stdlib.h>
#include <stdio.h>

const uint8_t ROWS = 4;
const uint8_t COLS = 4;
char keys[ROWS][COLS] = {
  { '1', '2', '3', 'A' },
  { '4', '5', '6', 'B' },
  { '7', '8', '9', 'C' },
  { '*', '0', '#', 'D' }
};

uint8_t colPins[COLS] = { 5, 4, 3, 2 }; // Pins connected to C1, C2, C3, C4
uint8_t rowPins[ROWS] = { 9, 8, 7, 6 }; // Pins connected to R1, R2, R3, R4

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

String v_passcode="";

LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

double *data;

void setup() {
  lcd.begin(16,2);
  lcd.setCursor(0,0);
  lcd.print("Enter number");
  lcd.setCursor(0,1);
  lcd.print("of elements.");
}


void loop() {
  int n;
  n = keypad.getKey(); //Storing Elements
  data = (double *)calloc(n, sizeof(double));

  if (n != NO_KEY){
    if (n == '0'){
      lcd.clear();
      lcd.begin(16,2);
      lcd.setCursor(0,0);
      lcd.print("Error! Memory");
      lcd.setCursor(0,1);
      lcd.print("not allocated.");
    }

  }

  if (n == 'D'){
    getnumber(n);
  }
  free(data);
}


void getnumber(int n){
  data = keypad.getKey();
  lcd.clear();
  lcd.begin(16,2);
  lcd.setCursor(0,0);
  lcd.print("Enter Numbers.");
    

  if (data == 'D'){
    //To compute the largest number
    for (int i = 1; i < n; ++i) {
    if (*data < *(data + i)) {
      *data = *(data + i);
      }
    }
      lcd.clear();
      lcd.begin(16,2);
      lcd.setCursor(0,0);
      lcd.print("Largest Number:");
      lcd.setCursor(0,1);
      lcd.print(*data);
    }
}