advent_of_code_2024/day_11/solution.go

package day_11

import (
	"strconv"
	"strings"
)

type Stones map[uint64]uint64

// task:https://adventofcode.com/2024/day/11
func SolveBasic(input string) int {
	stones := load(input)

	for i := 0; i < 25; i++ {
		stones = blink(stones)
	}

	sum := uint64(0)
	for _, st := range stones {
		sum += st
	}
	return int(sum)
}

// task:https://adventofcode.com/2024/day/11#part2
func SolveComplex(input string) int {
	stones := load(input)

	for i := 0; i < 75; i++ {
		stones = blink(stones)
	}

	sum := uint64(0)
	for _, st := range stones {
		sum += st
	}
	return int(sum)
}

func blink(before Stones) Stones {
	after := Stones{}
	for stone, count := range before {
		if stone == 0 {
			after[1] += count
		} else if val := fromUint(stone); len(val)%2 == 0 {
			after[parseUint(val[:len(val)/2])] += count
			after[parseUint(val[len(val)/2:])] += count
		} else {
			after[stone*2024] += count
		}
	}
	return after
}

func fromUint(stone uint64) string {
	return strconv.FormatUint(stone, 10)
}

func load(input string) Stones {
	stones := Stones{}
	for _, substring := range strings.Split(input, " ") {
		stones[parseUint(substring)]++
	}
	return stones
}

func parseUint(substring string) uint64 {
	if val, err := strconv.ParseUint(substring, 10, 64); err == nil {
		return val
	} else {
		panic(err)
	}
}