wirth-problem-15-12 in go

problem_15_12.go

package main

import (
	"log"
	"sort"
)

func generateSet(c chan<- int) {
	min := 0
	nums := make([]int, 0)
	nums = append(nums, 1)

	for len(nums) > 0 {
		// get the first num in slice. should be lowest num.
		i := nums[0]

		// have we already seen this number?
		if i > min {
			// nope, yield the number to the channel
			c <- i

			// update min so we'll skip this number if we have
			// a dupe in the nums slice
			min = i

			// add the next two numbers in the set
			nums = append(nums[1:], (2*i)+1, (3*i)+1)

			// sort
			sort.Ints(nums)
		} else {
			// already seen this number. pop first element off
			// slice and keep going
			nums = append(nums[1:])
		}
	}
}

// http://programmingpraxis.com/2012/12/07/wirth-problem-15-12/
func main() {
	// this solution uses a channel and goroutine as a
	// generator that yields the next value in the set
	c := make(chan int)
	go generateSet(c)

	// print the first 100 numbers in the set
	for i := 0; i < 100; i++ {
		log.Println(i, <-c)
	}
}