package main import ( "fmt" "math" "sort" "strings" h "git.bullercodeworks.com/brian/adventofcode/helpers" ) func main() { part1 := h.ArgIsSet("-1") justSort := h.ArgIsSet("-sort") input := h.StdinToStringSlice() var blacklists []Blacklist for i := range input { pts := strings.Split(input[i], "-") st := h.Atoi(pts[0]) end := h.Atoi(pts[1]) blacklists = append(blacklists, *CreateBlacklist(st, end)) } sort.Sort(ByStart(blacklists)) // Just output the sorted blacklists if justSort { for i := range blacklists { fmt.Print(blacklists[i].start, "-", blacklists[i].end, "\n") } return } // Find the lowest non-blacklisted IP if part1 { fmt.Println(findLowest(blacklists)) return } // Count how many IPs are allowed var numIps, blIdx, ip int highestIp := int(math.Pow(2, 32)) for ip <= highestIp { if blIdx >= len(blacklists) { break } if ip >= blacklists[blIdx].start { if ip <= blacklists[blIdx].end { ip = blacklists[blIdx].end + 1 continue } blIdx++ } else { numIps++ ip++ } } fmt.Println(numIps) } func findLowest(blacklists []Blacklist) int { var lowestIp int for i := range blacklists { if blacklists[i].hasIp(lowestIp) { lowestIp = blacklists[i].end + 1 } } return lowestIp } type Blacklist struct { start, end int } func CreateBlacklist(st, end int) *Blacklist { return &Blacklist{st, end} } func (b *Blacklist) hasIp(inp int) bool { return inp >= b.start && inp <= b.end } type ByStart []Blacklist func (b ByStart) Len() int { return len(b) } func (b ByStart) Swap(i, j int) { b[i], b[j] = b[j], b[i] } func (b ByStart) Less(i, j int) bool { return b[i].start < b[j].start }