#include <LiquidCrystal.h>

LiquidCrystal lcd(A0,A1,A2,A3,A4,A5);

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

int digit[ROWS][COLS]={
  {1, 2, 3, 12},
  {4, 5, 6, 13},
  {7, 8, 9, 14},
  {10, 0, 11, 15}
};

byte rowPins[] = {9, 8, 7, 6};
byte colPins[] = {5, 4, 3, 2};

int getDigit(){
  for (int c = 0; c < COLS; c++){
    digitalWrite(colPins[c], LOW);
    delay(1);
    for (int r = 0; r < ROWS; r++){
      if (digitalRead(rowPins[r]) == 0){
        while (digitalRead(rowPins[r]) == 0);
        return digit[r][c];
      }
    }
    digitalWrite(colPins[c], HIGH);
    delay(1);
  }
  return -1;
}

void setup() {
  lcd.begin(16,2);
  for (int c = 0; c < COLS; c++){
    pinMode(colPins[c], OUTPUT);
  }
  for (int r = 0; r < ROWS; r++){
    pinMode(rowPins[r], INPUT_PULLUP);
  }
}

void loop() {
  int a = getDigit();
  if (a != -1){
    lcd.print(a);
  }
}