adventoc/2024/day02.go

package adventoc2024

import (
	"bufio"
	"fmt"
	"io"
	"strings"
)

type Day2 struct{}

func (d Day2) Part1(r io.Reader) string {
	s := bufio.NewScanner(r)
	var sum int

	for s.Scan() {

		sz := strings.Count(s.Text(), " ") + 1

		level := make([]int, sz)
		levelprts := make([]any, sz)
		for i := range levelprts {
			levelprts[i] = &level[i]
		}

		fmt.Sscan(s.Text(), levelprts...)

		if layerOk(level) {
			sum++
		} else {
			reverse(level)
			if layerOk(level) {
				sum++
			}
		}
	}

	return printi(sum)
}

func (d Day2) Part2(r io.Reader) string {
	s := bufio.NewScanner(r)
	var sum int

	for s.Scan() {

		sz := strings.Count(s.Text(), " ") + 1

		level := make([]int, sz)
		levelprts := make([]any, sz)
		for i := range levelprts {
			levelprts[i] = &level[i]
		}

		fmt.Sscan(s.Text(), levelprts...)

		if layerOkWithDampen(level) {
			sum++
		} else {
			reverse(level)
			if layerOkWithDampen(level) {
				sum++
			}
		}

	}
	return printi(sum)
}

func inrange(i int) bool {
	return i < 4 && i > 0
}

func layerOk(layer []int) bool {
	for i := 0; i < len(layer)-1; i++ {
		if !inrange(layer[i] - layer[i+1]) {
			return false
		}
	}
	return true
}

func layerOkWithDampen(layer []int) bool {
	layerc := make([]int, len(layer)-1)
	for i := 0; i < len(layer)-1; i++ {
		if !inrange(layer[i] - layer[i+1]) {
			copy(layerc, layer[i:i+1])
			for i := range layer {
				copy(layerc, layer[:i])
				copy(layerc[i:], layer[i+1:])
				if layerOk(layerc) {
					return true
				}
			}
			return false
		}
	}
	return true
}