Monty Hall Problem

main.go

package main

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

var Swappers int
var Stayers int

func main() {

	// create a work group
	// set # of itterations
	var wg sync.WaitGroup
	simulations := 100000
	wg.Add(simulations)
	now := time.Now()

	for i := 0; i < simulations/2; i++ {
		go sim(true, &wg)
		go sim(false, &wg)
	}
	wg.Wait()

	x := PercentOf(Swappers, simulations/2)
	y := PercentOf(Stayers, simulations/2)
	timesince := time.Since(now).Seconds()

	fmt.Println("Running Threaded")
	fmt.Printf("Ran %v Simulations.  Took %.2v seconds\n", simulations, timesince)
	fmt.Printf("Those who swapped doors won %v percent of the time while those who did not only won %v percent\n", x, y)

	now = time.Now()
	wg.Add(simulations)
	Swappers, Stayers, x, y = 0, 0, 0, 0

	for i := 0; i < simulations/2; i++ {
		sim(true, &wg)
		sim(false, &wg)
	}
	wg.Wait()

	x = PercentOf(Swappers, simulations/2)
	y = PercentOf(Stayers, simulations/2)
	timesince = time.Since(now).Seconds()

	fmt.Println("Running Serial")
	fmt.Printf("Ran %v Simulations.  Took %.2v seconds\n", simulations, timesince)
	fmt.Printf("Those who swapped doors won %v percent of the time while those who did not only won %v percent\n", x, y)

}

// takes in s as a bool to determin if swapping doors
func sim(s bool, wg *sync.WaitGroup) {
	// close the Worker Group at end of execution
	defer wg.Done()

	// seed math/rand - deterministic result based on known seed but not important for this exercise.
	rand.Seed(time.Now().UTC().UnixNano())

	// randomly select which door is the winner
	winner := rand.Intn(3)
	doors := []int{0, 0, 0}
	doors[winner] = 1

	// randomly select which door the player picked
	selected := rand.Intn(3)

	// now assume we have eliminated a non-winning door, leaving only the winning door and a losing door - one of which has been selected by the player

	if s == true {
		// if we swap doors and our initially selected door was a loser than we return a winning 1
		if doors[selected] == 0 {
			Swappers = Swappers + 1
			//		fmt.Println("winner")
			return
		}
		//	fmt.Println("loser")
		return
	}

	if doors[selected] == 0 {
		// if we did not swap and the player did not select the winner then they lose.
		//	fmt.Println("loser")
		return
	}
	Stayers = Stayers + 1
	//fmt.Println("winner")
	return

}

func PercentOf(current int, all int) float64 {
	percent := (float64(current) * float64(100)) / float64(all)
	return percent
}