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

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

const byte ROWS = 4;
const byte COLS = 3;

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

byte colPins[COLS] = {4,5,6}; // Pins connected to C1, C2, C3, C4
byte rowPins[ROWS] = {0,1,2,3}; // Pins connected to R1, R2, R3, R4
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

String x = "";

void setup() {
  lcd.begin(16,2);
}

void loop() {
  // put your main code here, to run repeatedly:
  char key = keypad.getKey();
  if ((key!=NO_KEY)&&(key!='*')&&(key!='#')){
    lcd.setCursor(0,1);
    lcd.print(key);
    x += key;
    if (x.length()<=16){
      String y = Sort(x);
      lcd.setCursor(0,0);
      lcd.print(y);
    }
    else{
      x = "";
      lcd.clear();
    }
  }
}


String Sort(String x){
    if (x.length() <= 1){
      return x;
    }
    else{
      for(int j = 1; j < x.length(); j++){
        int key = x[j];
        int i = j - 1;
        while ((i>=0)&&(x[i])>key){
          x[i+1] = x[i];
          i -= 1;
        }
        x[i+1] = key;
      }
    }
    return x;
}