adventofcode/2024/02/main.go

package main

import (
	"aoc2024/helper"
	"fmt"
	"sort"
)

var reports [][]int

func main() {
	reports = helper.ReadLinesToIntArrays()

	// part 1
	save_count := 0
	for _, r := range reports {
		if isReportSave(r) {
			save_count++
		}
	}
	fmt.Printf("Save reports: %d\n", save_count)

	// part 2
	save_count = 0
	for _, r := range reports {
		if isReportSaveWithDamper(r) {
			save_count++
		}
	}
	fmt.Printf("Save reports (with damper): %d\n", save_count)
}

func isReportSaveWithDamper(report []int) bool {

	if isReportSave(report) {
		return true
	}

	for i := range report {
		// remove one item from report and try to validate
		new_report := removeFromSlice(report, i)
		if isReportSave(new_report) {
			return true
		}
	}

	return false
}

func removeFromSlice(slice []int, dropIndex int) []int {
	var newslice []int
	for i, v := range slice {
		if i != dropIndex {
			newslice = append(newslice, v)
		}
	}

	return newslice
}

func isReportSave(report []int) bool {

	if !isReportSorted(report) {
		return false
	}

	for i := range report {
		if (i + 1) < len(report) {
			if !isPairSave(report[i], report[i+1]) {
				return false
			}
		}
	}

	return true
}

func isReportSorted(slice []int) bool {
	ascSorted := sort.SliceIsSorted(
		slice,
		func(i, j int) bool { return slice[i] < slice[j] },
	)
	descSorted := sort.SliceIsSorted(
		slice,
		func(i, j int) bool { return slice[i] > slice[j] },
	)

	return ascSorted || descSorted

}

func isPairSave(x int, y int) bool {
	if x == y {
		return false
	}
	diff := helper.Abs(x - y)
	if diff > 3 {
		return false
	}
	return true
}