The Monty Hall Problem - brute force proof

the_monty_hall_problem.js

const CHANCE = 3;

function rollDoor() {
    return Math.floor(Math.random() * CHANCE);
}

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

function removeRandom(arr, hidden, choosen) {
    if (hidden !== choosen) {
        return [arr[hidden], arr[choosen]];
    }

    const variants = [];
    for (let i = 0; i < arr.length; i++) {
        if (hidden === i || choosen === i) {
            continue;
        }

        variants.push(arr[i]);
    }

    return [arr[hidden], randArr(variants)];
}

function game(do_choose = false, times = 100000) {
    const stat = {
        'count': times,
        'win': 0,
        'lose': 0
    };

    for (let i = 0; i < times; i++) {
        const variants = [1, 2, 3];

        const hidden = rollDoor();
        const choosen = rollDoor();

        // remove 1 door
        const variants2 = removeRandom(variants, hidden, choosen);

        if (do_choose) {
            let new_choosen = -1;

            for (let i = 0; i <= variants2.length; i++) {
                if (variants[choosen] !== variants2[i]) {
                    new_choosen = variants2[i];
                    break;
                }
            }

            if (variants[hidden] === new_choosen) {
                stat['win']++;
            } else {
                stat['lose']++;
            }

            continue;
        }

        if (choosen === hidden) {
            stat['win']++;
        } else {
            stat['lose']++;
        }
    }

    return stat;
}

const stat = game();
console.log('------ No Change -------');
console.log(`Count: ${stat['count']}, Win: ${stat['win']}, Lose: ${stat['lose']}`);

const stat2 = game(true);
console.log('------- New Door -------');
console.log(`Count: ${stat2['count']}, Win: ${stat2['win']}, Lose: ${stat2['lose']}`);