Simulates Josephus problem solution using Goroutines and Channels

josephus_using_channels_goroutines.go

package main

import (
	"fmt"
	"time"
)

type Command struct {
	message  string
	senderId int
}

func main() {
	prev := make(chan Command)
	last := prev
	n := 1000

	for i := 0; i < n - 1; i++ {
		next := make(chan Command)
		go process(i, prev, next)
		prev = next
	}
	go process(n - 1, prev, last)
	last <- Command{message:"Start", senderId: -1}
	time.Sleep(time.Second)
}

/*func hardcodedJosephusRingFor4People() {
	chan1 := make(chan Command)
	chan2 := make(chan Command)
	chan3 := make(chan Command)
	chan4 := make(chan Command)

	go process(0, chan4, chan1)
	go process(1, chan1, chan2)
	go process(2, chan2, chan3)
	go process(2, chan3, chan4)

	chan4 <- Command{message:"Start", senderId: -1}
	time.Sleep(time.Second)
}*/

func process(id int, left, right chan Command) {
	alive := true
	for {
		command := <-left
		//fmt.Printf("%+v\n", command)
		if command.message == "Start" {
			right <- Command{message:"kill", senderId:id}
		} else if command.message == "kill" && alive {
			//fmt.Printf("killing %d and passing sword\n", id)
			alive = false
			right <- Command{message:"passSword", senderId: command.senderId}
		} else if command.message == "kill"  && !alive && command.senderId == id {
			continue
		} else if command.message == "kill"  && !alive {
			right <- Command{message:"kill", senderId: command.senderId}
		} else if command.message == "passSword" && alive && command.senderId == id {
			fmt.Println("Survivor is", id)
		} else if command.message == "passSword" && alive {
			//fmt.Printf("%d has sword. kill next\n", id)
			right <- Command{message:"kill", senderId:id}
		} else if command.message == "passSword" && !alive {
			right <- Command{message:"passSword", senderId:command.senderId}
		}
	}
}