aoc2023/day-8/two.go

package main

import (
	"strings"
)

// GCF returns the greatest common factor of two numbers
func GCF(a, b int) int {
	for b != 0 {
		t := b
		b = a % b
		a = t
	}
	return a
}

// LCM returns least common multiple of a set of numbers
func LCM(a, b int, integers ...int) int {
	result := a * b / GCF(a, b)

	for i := 0; i < len(integers); i++ {
		result = LCM(result, integers[i])
	}

	return result
}

// two returns minimum steps required until all routes end with '*Z'
func two(lines []string) int {
	parselines(lines)

	startpoints := make([]string, 0)
	for k := range steps {
		if strings.HasSuffix(k, "A") {
			startpoints = append(startpoints, k)
		}
	}

	nums := []int{}
	for _, step := range startpoints {
		num := 0
		for i := 0; !strings.HasSuffix(step, "Z"); i, num = i+1, num+1 {
			if i == len(directions) {
				i = 0
			}
			if directions[i] == 'L' {
				step = steps[step][LEFT]
			} else {
				step = steps[step][RIGHT]
			}
		}
		nums = append(nums, num)
	}

	lcm := 0
	lcm = LCM(nums[0], nums[1], nums[2:]...)

	return lcm
}