hannibals_problem.js

// Mathematics.  The problem of Hannibal's organs
// https://twitter.com/pickover/status/1618030222246580224

let JAR = []
let BRAIN = 0
let KIDNEY = 1

// Random add a brain or a kidney
function init() {
    JAR = []
    Math.random() > 0.5 ? JAR.push(BRAIN) : JAR.push(KIDNEY)
}

// Add a brain
function addBrain() {
    JAR.push(BRAIN)
}

// Draw from JAR, remove element and return element
function draw() {
    let index = Math.floor(Math.random()*JAR.length)
    let draw = JAR[index];
    JAR.splice(index, 1)
    return draw
}

let BRAINS_DRAWN = 0
let KIDNEYS_DRAWN = 0
let NUM_TESTS = 10000
let USABLE_TESTS = 0
for(let i = 0; i < NUM_TESTS; i++) {

    init()
    addBrain()
    
    // Hanibal draws
    // If it is not a brain then the expiriment will not be used. 
    let res = draw()
    if (res !== BRAIN) {
        continue;
    }

    USABLE_TESTS +=1
    res = draw()
    
    if (res === BRAIN) {
        BRAINS_DRAWN += 1
    }
    if (res === KIDNEY) {
        KIDNEYS_DRAWN += 1
    }
}

console.log(`Chance of a usable test `, USABLE_TESTS / NUM_TESTS)
console.log(`Chance of drawing a BRAIN out of ${USABLE_TESTS}`, BRAINS_DRAWN / USABLE_TESTS)
// -> about 2/3 ~ 0.66....
console.log(`Chance of drawing a KIDNEY out of ${USABLE_TESTS}`, KIDNEYS_DRAWN / USABLE_TESTS)
// -> about 1/3 ~ 0.33....