advent of code 2021 day 14 in golang

14.go

package main

import (
	"math"
	"strings"
)

const data = `
`

func main() {
	ss := strings.Split(strings.Trim(data, " \n"), "\n\n")
	tmpl := ss[0]

	rules := make(map[[2]byte]byte)
	for _, inst := range strings.Split(ss[1], "\n") {
		rules[[2]byte{inst[0], inst[1]}] = inst[6]
	}

	sPairs := make(map[[2]byte]int)
	for i := 0; i+1 < len(tmpl); i += 1 {
		sPairs[[2]byte{tmpl[i], tmpl[i+1]}] += 1
	}

	for step := 1; ; step += 1 {
		newPairs := make(map[[2]byte]int)

		for pair, val := range sPairs {
			if ins, ok := rules[pair]; ok {
				newPairs[[2]byte{pair[0], ins}] += val
				newPairs[[2]byte{ins, pair[1]}] += val
			} else {
				newPairs[pair] += val
			}
		}

		sPairs = newPairs

		if step == 40 {
			break
		}
	}

	letterCount := make(map[byte]int)
	for pair, count := range sPairs {
		letterCount[pair[0]] += count
	}
	letterCount[tmpl[len(tmpl)-1]] += 1

	max := 0
	min := math.MaxInt64

	for _, count := range letterCount {
		if count > max {
			max = count
		}
		if count < min {
			min = count
		}
	}

	println(max - min)
}