ballclock.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
)

type Output struct {
	balls int
	minutes int
}

func main() {
	if len(os.Args) < 2 {
		log.Printf("usage: %s configfile\n", os.Args[0])
		os.Exit(1)
	}

	file, err := os.Open(os.Args[1])
	defer file.Close()

	if err != nil {
		log.Fatal(err)
	}

	scanner := bufio.NewScanner(file)

	clocks := 0;
	c := make(chan Output)

	for scanner.Scan() {
		balls, err := strconv.Atoi(scanner.Text())

		if err != nil {
			log.Fatal(err)
		}

		if balls == 0 {
			break
		}

		if balls < 27 || balls > 127 {
			log.Fatalf("bad number of balls: %d (0, 27 - 127 allowed)", balls)
		}

		clocks++;

		go makeAndRunClock(balls, c)
	}

	if scanner.Err() != nil {
		log.Fatal(err)
	}

	for i := 0; i < clocks; i++ {
		output := <-c
		fmt.Printf("%d balls cycle after %d days (%d minutes).\n", output.balls, output.minutes/(60*24), output.minutes)
	}
}

type Ball struct {
	id int
	next *Ball
}

func listToSlice(head *Ball) []int {
	s := make([]int, 0)
	for ; head != nil ; head = head.next {
		s = append(s, head.id)
	}
	return s
}

func makeAndRunClock(balls int, c chan Output) {
	var minute, five, hour, bottom, last, cur *Ball
	var ball int

	minutes := 1
	mCount := 1
	fCount := 0
	hCount := 0
	bCount := balls - 1

	for ball = 0; ball < balls; ball++ {
		if bottom == nil {
			bottom = &Ball{ball, nil}
			last = bottom
			continue
		}
		last.next = &Ball{ball, nil}
		last = last.next
	}

	minute = bottom
	bottom = bottom.next
	minute.next = nil

	for {
		//fmt.Printf("minute %d:\n\tmin:  %v\n\tfive: %v\n\thour: %v\n\tbot:  %v\n",
			//minutes, listToSlice(minute), listToSlice(five), listToSlice(hour), listToSlice(bottom));
		if bCount == balls {
			for ball, cur = 0, bottom; cur != nil && cur.id == ball; ball++ {
				cur = cur.next
			}
			if ball == balls {
				break
			}
		}

		minutes++

		cur = bottom
		bottom = bottom.next
		cur.next = nil
		bCount--

		if mCount != 4 {
			cur.next = minute
			minute = cur
			mCount++
			continue
		}

		last.next = minute
		last = minute.next.next.next
		minute = nil
		mCount = 0
		bCount += 4

		if fCount != 11 {
			cur.next = five
			five = cur
			fCount++
			continue
		}

		last.next = five
		last = five.next.next.next.next.next.next.next.next.next.next
		five = nil
		fCount = 0
		bCount += 11

		if hCount != 11 {
			cur.next = hour
			hour = cur
			hCount++
			continue
		}

		last.next = hour
		last = hour.next.next.next.next.next.next.next.next.next.next
		last.next = cur
		last = cur
		hour = nil
		hCount = 0
		bCount += 12
	}

	c <- Output{balls, minutes}
}