sim.js

const groupCount = 5
function sim() {
    let score = {}
    for (let i = 0; i < groupCount; i++) {
        score[i] = 0
    }

    for (let i = 0; i < groupCount - 1; i++) {
        for (let j = i + 1; j < groupCount; j++) {
            const win1 = Math.random() < 0.5
            const isKO = Math.random() < 0.01
            const winS = isKO ? 3 : 2
            const lostS = -1
            if (win1) {
                score[i] += winS // win
                score[j] += lostS // lost
            } else {
                score[j] += winS // win
                score[i] += lostS // lost
            }
        }
    }

    const ss = [...Object.values(score)]
    
    let max = 0
    const repeatTimes = ss.map(i => [i, ss.filter(j => j === i).length])
    for (let [s, r] of repeatTimes) {
        max = Math.max(r, max)
    }
    return max
}

function test() {
    const round = 1000000
    let total = {}
    for (let c = 0; c < round; c++) {
        const r = sim()
        total[r] = (total[r] || 0) + 1
    }
    
    let result = {}
    for (let i of Object.keys(total)) {
        result[i] = total[i] / round
    }
    
    console.log(result)
}

test()