aoc2024/day-02/internal/two/solve.go

package two

import (
	"bufio"
	"bytes"
	"io"
)

type comparator func([]int, int) bool
type dampener func([]int, comparator, int) bool

func Solve(buf []byte) (int, error) {
	r := bytes.NewReader(buf)
	sum, err := parseLines(r)
	if err != nil {
		return 0, err
	}

	return sum, nil
}

func parseLines(r io.Reader) (int, error) {
	var (
		cmpIncrease = func(nums []int, i int) bool {
			return nums[i-1] >= nums[i]
		}

		cmpDecrease = func(nums []int, i int) bool {
			return nums[i-1] <= nums[i]
		}
	)

	var sum int

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		nums := intsFromString(scanner.Text())

		if check(withDampener, nums, cmpIncrease) || check(withDampener, nums, cmpDecrease) {
			sum++
		}
	}

	if err := scanner.Err(); err != nil {
		return 0, err
	}

	return sum, nil
}

func check(fn dampener, nums []int, cmp comparator) bool {
	var count int
	return fn(nums, cmp, count)
}