2021-advent-14.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"math"
	"strings"
)

func readLine(input string) ([]string, map[string]string) {
	bytes, err := ioutil.ReadFile(input)
	if err != nil {
		log.Fatal(err)
	}
	lines := strings.Split(string(bytes), "\n")
	chain := make([]string, 0, len(lines[0]))
	for _, v := range lines[0] {
		chain = append(chain, string(v))
	}
	transformations := make(map[string]string)
	for _, v := range lines[2:] {
		tmp := strings.Split(v, " -> ")
		transformations[tmp[0]] = tmp[1]
	}
	return chain, transformations
}

func task1step(chain []string, transformations map[string]string) []string {
	nextChain := make([]string, 0, 2*len(chain))
	nextChain = append(nextChain, chain[0])
	for i := 0; i < len(chain)-1; i++ {
		key := chain[i] + chain[i+1]
		nextChain = append(nextChain, transformations[key], chain[i+1])
	}
	return nextChain
}

func printChain(chain []string) {
	for _, v := range chain {
		fmt.Print(v)
	}
	fmt.Println()
}

func task1(input string) {
	chain, transformations := readLine(input)
	// printChain(chain)

	var nextChain []string = chain
	steps := 10
	for i := 1; i <= steps; i++ {
		nextChain = task1step(nextChain, transformations)
		// printChain(nextChain)
	}

	min := math.MaxInt
	minS := ""
	max := -1
	maxS := ""
	counts := make(map[string]int)
	for _, v := range nextChain {
		counts[v]++
	}
	for k := range counts {
		if counts[k] < min {
			min = counts[k]
			minS = k
		}
		if counts[k] > max {
			max = counts[k]
			maxS = k
		}
	}
	fmt.Printf("Day 14 task 1 input: %v\n", input)
	fmt.Printf("min: %v\n", min)
	fmt.Printf("max: %v\n", max)
	fmt.Printf("(max-min): %v\n", (max - min))
	fmt.Printf("minS: %v maxS: %v\n", minS, maxS)
}

func task2(input string) {
	chain, transformations := readLine(input)
	adjacentTracker := make(map[string]int)
	counts := make(map[string]int)
	counts[chain[0]]++
	for i := 0; i < len(chain)-1; i++ {
		key := chain[i] + chain[i+1]
		adjacentTracker[key] += 1
		counts[chain[i+1]]++
	}
	min := math.MaxInt
	minS := ""
	max := -1
	maxS := ""

	steps := 40
	for i := 1; i <= steps; i++ {
		nextTracker := make(map[string]int)
		for k, val := range adjacentTracker {
			newItem := transformations[k]
			left := string(k[0]) + newItem
			right := newItem + string(k[1])
			counts[newItem] += val
			nextTracker[left] += val
			nextTracker[right] += val
		}
		adjacentTracker = nextTracker
	}

	for k := range counts {
		if counts[k] < min {
			min = counts[k]
			minS = k
		}
		if counts[k] > max {
			max = counts[k]
			maxS = k
		}
	}
	fmt.Printf("Day 14 task 2 input: %v\n", input)
	fmt.Printf("min: %v\n", min)
	fmt.Printf("max: %v\n", max)
	fmt.Printf("(max-min): %v\n", (max - min))
	fmt.Printf("minS: %v maxS: %v\n", minS, maxS)
}

func main() {
	task1("example.txt")
	task1("input.txt")
	task2("example.txt")
	task2("input.txt")
}