Debouncer arduLino with millis()

#include<LiquidCrystal.h>
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
int brojac;
byte stanje_tastera;
byte blokiraj;
unsigned long poslednja_promena;


#define SELECT 1
#define LEFT 2
#define DOWN 4
#define UP 3
#define RIGHT 5
#define NONE 0

byte ocitajTaster(int ulaz){
  if(ulaz < 800){
    if(ulaz >550){
      return SELECT;
    }else{
      if(ulaz>350){
        return LEFT;
      }else{
       if(ulaz>200){
        return DOWN;
       }else{
        if (ulaz>50){
          return UP;
        }else{
          return RIGHT;
        }
       }
      }
    }
  }else{
    return NONE;
  }

}

void ispisTastera(byte ulaz){
  lcd.setCursor(0,0);
  switch(ulaz){
    case 0: lcd.clear();break;
    case 1: lcd.print("SELECT");break;
    case 2: lcd.print("LEFT");break;
    case 3: lcd.print("UP");break;
    case 4: lcd.print("DOWN");break;
    case 5: lcd.print("RIGHT");break;
  }
}

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

}
void loop(){
  if(stanje_tastera !=ocitajTaster(analogRead(0))){
    stanje_tastera = ocitajTaster(analogRead(0));
    blokiraj = 0;
  }
  if((millis()- poslednja_promena>50 )&&(blokiraj==0)){
    blokiraj =1 ;

  switch(ocitajTaster(analogRead(0))){
    case SELECT: brojac = 0; break;
    case UP:  brojac++; break;
    case DOWN: brojac--; break;
  }
  lcd.clear();
  lcd.print(brojac);
  }}