// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0; // will store last time LED was updated

// constants won't change:
const long interval = 500; // interval at which to blink (milliseconds)

int pushButton1 = 2;
int pushButton2 = 4;
int pushButton3 = 6;
int pushButton4 = 11;

int buttons[4] = {
  pushButton1,
  pushButton2,
  pushButton3,
  pushButton4
};

void setup() {
  // set the digital pin as output:
  Serial.begin(9600);
  pinMode(pushButton1, OUTPUT);
  digitalWrite(pushButton1, LOW);
  pinMode(pushButton2, INPUT_PULLUP);
  pinMode(pushButton3, INPUT_PULLUP);
  pinMode(pushButton4, INPUT_PULLUP);
}

bool testConnection2(int A, int B) {
  for (int i = 0; i < 4; i++) {
    if (i == A) {
      pinMode(buttons[i], OUTPUT);
      digitalWrite(buttons[i], LOW);
    } else {
//      digitalWrite(buttons[i], HIGH);
      pinMode(buttons[i], INPUT_PULLUP);
    }
  }
//  delay(10);

  if (!digitalRead(buttons[B])) {
    return true;
  } else {
    return false;
  }
}
bool testConnection(int A, int B) {
  return testConnection2(A, B) && testConnection2(B, A);
}

// int lastNumber = -1;

void loop() {

  if (testConnection(0, 1)) {
//    if (lastNumber != 01) {
//      lastNumber = 01;
      Serial.println("0011");
//    }
  } else if (testConnection(0, 2)) {
//    if (lastNumber != 02) {
//      lastNumber = 02;
      Serial.println("0101");
//    }
  } else if (testConnection(0, 3)) {
//    if (lastNumber != 03) {
//      lastNumber = 03;
      Serial.println("1001");
//    }
  } else if (testConnection(1, 2)) {
//    if (lastNumber != 12) {
//      lastNumber = 12;
      Serial.println("0110");
//    }
  } else if (testConnection(1, 3)) {
//    if (lastNumber != 13) {
//      lastNumber = 13;
      Serial.println("1010");
//    }
  } else if (testConnection(2, 3)) {
//    if (lastNumber != 23) {
//      lastNumber = 23;
      Serial.println("1100");
//    }
//  } else {
//    if (lastNumber != 0) {
//      lastNumber = 0;
//      Serial.println("0000");
//    }
  }
}

/*
  
  for (int ii = 0; ii < 4; ii++)
  {
    for (int jj = 0; jj < 4; jj++)
    {
      if (jj == ii)
      {
        pinMode(buttons[jj], OUTPUT);
        digitalWrite(buttons[jj], LOW);  
      }
      else
      {
        pinMode(buttons[jj], INPUT_PULLUP);
      }
    }
    for (int jj = ii; jj < 4; jj++)
    {
      if (!(ii == jj) && !digitalRead(buttons[jj]))
      {
        for (int kk = 3; kk >= 0; kk--)
        {
          if (kk == ii || kk == jj)
          {
            Serial.print(1);
          }
          else
          {
            Serial.print(0);
          }
        }
        Serial.print("\n");
        received_input = true;
        break;
      }
   }
   
    
  //  if (received_input)
  //  {
   //   break;
   // }
  }
  */