#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>

LiquidCrystal_I2C lcd(0x27,20,4);
int i = 0;

const int ROW_NUM = 4;
const int COLUMN_NUM = 4;

byte pin_rows[ROW_NUM] = {9, 8, 7, 6};
byte pin_column[COLUMN_NUM] = {5, 4, 3, 2};

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

Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );

char key;



void setup() {
  lcd.init();                 
  lcd.backlight();             
  lcd.home();  
  Serial.begin(9600);
}

void loop() {
  int num_item;
  double *data, *reset;

  boolean valid = false; 

  while(!num_item){
    lcd.setCursor(0,0);
    lcd.print("Input value of");
    lcd.setCursor(0,1);
    lcd.print("    items: ");
    key = keypad.getKey();
    
    if (key){
     if(checkIfNum(key) and key != '0'){
      num_item = String(key).toInt();
      data = (double *)malloc(num_item);
      lcd.clear();
     }
     else{
      validNumber();
    
      }
      
    }

  }

  for (int i = 0; i < num_item; ++i) {
   valid = false;
  while(!valid){
    lcd.setCursor(0,0);
    lcd.print(" No. of input ");
    lcd.print(i+1);
    lcd.setCursor(0,1);
    lcd.print("   out of ");
    lcd.print(num_item);
    key = keypad.getKey();
    if(key){
      if(checkIfNum(key)){
      int ascii = key;
      data[i] = ascii -48;
      valid = true;
      }
      else {
      validNumber();
      }

    }
 
  }

  lcd.clear();

  }

  for (int i = 0; i < num_item; ++i) {
  if (*data < *(data + i)){
    *data = *(data + i);
    }
    
  }
  
  lcd.setCursor(0,0);
  lcd.print("  The highest");
  lcd.setCursor(0,1);
  lcd.print(" value is: ");
  lcd.print(*data);
  free(data);
  delay(5000);
  lcd.clear();


}

boolean checkIfNum(char input_char){
  if(input_char == 'A' or input_char == 'B' or input_char == 'C' or input_char == 'D' or input_char == '*' or input_char == '#'){
    return false;
  }
  else{
    return true;
  }
  
}

void validNumber(){
lcd.clear();
lcd.setCursor(0,0);
lcd.print(" Please input a");
lcd.setCursor(0,1);
lcd.print("  valid number!");
delay(2000);
lcd.clear();

}