// A Monty Hall Problem Simulation
// https://wokwi.com/projects/472906781803671553
// for https://forum.arduino.cc/t/the-monty-hall-problem/1456367/152

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);

  Serial.print("Press any key to randomize");
  while(!Serial.available() ) ;
  int key = Serial.read();
  randomSeed(random()+micros());
}

long gameCount = 0;
long stayWins = 0;
long switchWins = 0;
long postMontyWins = 0;
long trials = 1000;


void loop() {
  char prizes[]= "CER";  // Car, Ewe, Ram
  if(trials){
    --trials;
    scrambleString(prizes);
    //Serial.println(prizes);

    int carDoorChoice = random(3); // which door is the car hidden behind?
    int stayDoorChoice = random(3); // Which door does the "Stay" layer choose  
    int goatChoice = random(2); // 1st or second goat, if two goats unchoses
    int postMontyChoice = random(2); //  one of the two remaining doors
    ++gameCount;
    
    char tmp = prizes[carDoorChoice];
    int montyOpens = -1;
    int switchDoorChoice = -1;
    if (prizes[stayDoorChoice] == 'C' ){
      ++stayWins;
      // two goats for Monty to choose
      switch (stayDoorChoice){
        case 0: montyOpens = goatChoice==0? 1 :2; break;
        case 1: montyOpens = goatChoice==0? 0 :2; break;
        case 2: montyOpens = goatChoice==0? 0 :1; break;
      }
      if (postMontyChoice == 0) ++postMontyWins;
    }
    else // stay chose a goat
    {
    switch (stayDoorChoice){
        case 0: montyOpens = prizes[1]!='C'? 1:2; 
          switchDoorChoice = montyOpens==1? 2:1;
          break;
        case 1: montyOpens = prizes[0]!='C'? 0:2;
          switchDoorChoice = montyOpens==0? 2:0;
          break;
        case 2: montyOpens = prizes[0]!='C'? 0:1;
          switchDoorChoice = montyOpens==0? 1:0;
          break;
      }

      ++switchWins;
      if (postMontyChoice == 1) ++postMontyWins;
    }
    Serial.print(" Trial:");
    Serial.print(gameCount);
    Serial.print(" prizes:");
    Serial.print(prizes);
    Serial.print(" Stay:");
    Serial.print(stayDoorChoice+1);
    Serial.print(" Monty:");
    Serial.print(montyOpens+1);
    Serial.print(" Switch:");
    Serial.print(switchDoorChoice+1);

    Serial.print(" stay%=");
    Serial.print(100.0*stayWins/gameCount);
    Serial.print(" switch%=");
    Serial.print(100.0*switchWins/gameCount);
    Serial.print(" random%=");
    Serial.print(100.0*postMontyWins/gameCount);
    
    Serial.println();
  }
}

void scrambleString(char* string){
  unsigned length = strlen(string);
  for (int i = 0; i < length; i++)
  {
    int random_index = rand() % length; // 0 ... length-1
    
    char temp = string[random_index];
    string[random_index] = string[i];
    string[i] = temp;
  }
}

void BADscrambleString(char* str){
  //oops -- don't reinvent the wheel
  unsigned ll = strlen(str)-1;
  for(long ii = ll; ii >0 ; --ii){
    int ind = random(ii);
    char temp = str[ind];
    str[ind]= str[ll];
    str[ll] = temp;
  }
}