IBM Challenge May 2017 (CABACB)

main.go

package main

import (
	"os"
)

const (
	CHARS_COUNT = 20
	LEN         = CHARS_COUNT*2 + 1
)

var str = make([]int, LEN)
var symbols = make([]bool, CHARS_COUNT+1)
var dash = false

func main() {
	run(0)
}

func run(index int) {
	if index == LEN {
		printResult()
		return
	}

	if str[index] != 0 {
		run(index + 1)
		return
	}

	for i := 1; i <= CHARS_COUNT; i++ {
		if index+i+1 >= LEN {
			break
		}

		if symbols[i] == false && str[index+i+1] == 0 {
			symbols[i] = true

			str[index] = i
			str[index+i+1] = i

			run(index + 1)

			symbols[i] = false
			str[index] = 0
			str[index+i+1] = 0
		}
	}

	if dash == false && index > 0 {
		str[index] = 45
		dash = true

		run(index + 1)

		str[index] = 0
		dash = false
	}
}

func printResult() {
	for _, char := range str {
		if char != 45 {
			char += 64
		}

		os.Stdout.WriteString(string(char))
	}

	os.Stdout.WriteString("\n")
}