function randomChoice(arr){
    return arr[Math.floor(Math.random() * arr.length)];
}


function pickAndStay(doors, prize) {
    // Player selects a door.
    let playerSelection = randomChoice(doors);

    // Monty reveals a door you did not select.
    let montyReveals = randomChoice(doors);
    while(montyReveals === playerSelection) {
        montyReveals = randomChoice(doors);
    }

    // If player selected the answer player wins (+1) else loss.
    return playerSelection === prize ? 1 : 0;
}


function pickAndSwitch(doors, prize) {
    // Player selects a door.
    let playerSelection = randomChoice(doors);

    // Monty reveals a door you did not select and Monty does not reveal the prize (by coincidence, not by his knowledge).
    let montyReveals = randomChoice(doors);
    while(montyReveals === playerSelection || montyReveals === prize) {
        montyReveals = randomChoice(doors);
    }

    // Player switches, so they get the prize if their first selection is not the answer.
    return playerSelection !== prize ? 1 : 0;
}

function trials(n, fn) {
    // Run n trials of strategy defined by function fn and return number of prizes obtained.
    const doors = [0,1,2];
    let total = 0;
    for(let i = 0; i < n; i ++) {
        let prize = randomChoice(doors);
        total += fn(doors, prize);
    }

    return total;
}