https://twitter.com/littmath/status/1769044719034647001

coinflips.go

package main

import (
	"fmt"
	"math/rand"
	"sync"

	"gonum.org/v1/gonum/stat"
)

func main() {

	simulations := 1000000
	flips := 100

	var wg sync.WaitGroup
	resultsChan := make(chan []int, simulations)

	for i := 0; i < simulations; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			alice, bob := runSimulation(flips)
			resultsChan <- []int{alice, bob}
		}()
	}

	wg.Wait()
	close(resultsChan)

	var aliceWins, bobWins, ties int
	var alicePoints, bobPoints []float64

	for result := range resultsChan {
		alice, bob := result[0], result[1]
		alicePoints = append(alicePoints, float64(alice))
		bobPoints = append(bobPoints, float64(bob))

		if alice > bob {
			aliceWins++
		} else if bob > alice {
			bobWins++
		} else {
			ties++
		}
	}

	fmt.Printf("Simulations: %d\n", simulations)
	fmt.Printf("Alice wins: %d\n", aliceWins)
	fmt.Printf("Bob wins: %d\n", bobWins)
	fmt.Printf("Ties: %d\n", ties)

	fmt.Printf("Alice's average points: %.2f\n", stat.Mean(alicePoints, nil))
	fmt.Printf("Bob's average points: %.2f\n", stat.Mean(bobPoints, nil))
	fmt.Printf("Alice's standard deviation: %.2f\n", stat.StdDev(alicePoints, nil))
	fmt.Printf("Bob's standard deviation: %.2f\n", stat.StdDev(bobPoints, nil))
}

func runSimulation(flips int) (int, int) {
	alice := 0
	bob := 0

	prev := ""
	for i := 0; i < flips; i++ {
		flip := "H"
		if rand.Float64() < 0.5 {
			flip = "T"
		}

		if prev == "H" {
			if flip == "T" {
				bob++
			} else {
				alice++
			}
		}

		prev = flip
	}

	return alice, bob
}