main.go

package main

import (
	"fmt"

	aoc "github.com/shraddhaag/aoc/library"
)

func main() {
	input := aoc.ReadFileLineByLine("input.txt")

	getTotalSafeReportCount(input)
}

func isReportSafe(reportNum []int) bool {
	flagIncrease, flagDecrease := false, false

	for i := 1; i < len(reportNum); i++ {
		diff := reportNum[i] - reportNum[i-1]

		if diff > 0 {
			flagIncrease = true
		} else if diff < 0 {
			flagDecrease = true
		} else {
			return false
		}

		if flagDecrease && flagIncrease {
			return false
		}

		if diff > 3 || diff < -3 {
			return false
		}
	}

	return true
}

func checkReportSafetyWithDeletion(reportNum []int) bool {

	for i := 0; i < len(reportNum); i++ {
		isSafe := isReportSafeWithDeletion(reportNum, i)
		if isSafe {
			return true
		}
	}

	return false
}

func isReportSafeWithDeletion(report []int, deleteIndex int) bool {
	copyReport := make([]int, len(report))
	copy(copyReport, report)

	if deleteIndex == len(copyReport)-1 {
		copyReport = copyReport[:deleteIndex]
	} else {
		copyReport = append(copyReport[:deleteIndex], copyReport[deleteIndex+1:]...)
	}
	return isReportSafe(copyReport)
}

func getTotalSafeReportCount(reports []string) int {
	var count int
	var countWithDeletion int
	for _, report := range reports {
		reportNum := aoc.FetchSliceOfIntsInString(report)

		if isReportSafe(reportNum) {
			count++
		} else if checkReportSafetyWithDeletion(reportNum) {
			countWithDeletion++
		}
	}
	fmt.Printf("answer for part 1: %d\nanswer for part 2: %d\n", count, count+countWithDeletion)
	return count
}