Arduino LCD Digital Input Counter -

i have arduino lcd , 1 spdt switch connected board. the common pin of spdt grounded , outer pins each connected digital input. program should increment , decrement counter being printed lcd screen. have 1 input working increments counter not know how implement code input decrement counter. code posted below.

thank you

 #include <liquidcrystal.h>    liquidcrystal lcd(12, 11, 5,4,3,2);     const byte buttonpin = 8;      int counter = 0;             // set counter 0 begin    byte buttonstate;             // current reading input pin  byte lastbuttonstate = high;   // previous reading input pin   unsigned long lastdebouncetime = 0;    unsigned long debouncedelay = 50;     void setup()   {  serial.begin(9600);    pinmode(buttonpin, input_pullup);   lcd.begin(16, 2);           //  2x16 lcd display  }  void loop() {  // read state of switch local variable:  byte reading = digitalread(buttonpin);   // check see if pressed button  // (i.e. input went high low),  , you've waited  // long enough since last press ignore noise:   // if switch changed, due noise or pressing:  if (reading != lastbuttonstate) {   // reset debouncing timer   lastdebouncetime = millis();   }    if ((millis() - lastdebouncetime) >= debouncedelay) {   // whatever reading at, it's been there longer   // debounce delay, take actual current state:      // if button state has changed:     if (reading != buttonstate) {     buttonstate = reading;      if (buttonstate == low) {        counter ++;     serial.println(counter);       lcd.setcursor(0, 1);     lcd.print(counter);   }     }  }  lastbuttonstate = reading;   } 

you cannot connect 1 pole of switch input pin other ground. detect low when when suppose detect high on pin, floating. connect pull-up resistor input pins.

or can use pinmode(inpin, input_pullup);

this pull input pin high internally , can detect swithces , implememnt code.