Add day 4 solution, part 1.
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aff2172b40
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140
2018/day04-1.go
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140
2018/day04-1.go
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package main
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import (
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"fmt"
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"sort"
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"strconv"
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"strings"
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"time"
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"internal/util"
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)
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func main() {
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data := util.ReadInput()
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shifts := ParseInput(data)
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guards := BuildGuards(shifts)
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sleepiest, sleepiestMinute := FindSleepiestData(guards)
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fmt.Printf("Sleepiest Guard: %d\n", sleepiest.id)
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fmt.Printf("Sleepiest Minute: %d\n", sleepiestMinute)
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fmt.Printf("Result: %d\n", sleepiest.id*sleepiestMinute)
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}
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func FindSleepiestData(guards map[int]*Guard) (*Guard, int) {
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var sleepiest *Guard
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for _, guard := range guards {
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if sleepiest == nil {
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sleepiest = guard
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continue
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}
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if guard.sleepTotal > sleepiest.sleepTotal {
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sleepiest = guard
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}
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}
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sleepiestMinute := -1
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sleepiestCount := 0
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for minute, sleepiness := range sleepiest.sleep {
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if sleepiness > sleepiestCount {
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sleepiestCount = sleepiness
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sleepiestMinute = minute
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}
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}
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return sleepiest, sleepiestMinute
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}
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type Guard struct {
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id int
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sleep [60]int
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sleepTotal int
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}
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type SleepEvent struct {
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start, end int
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}
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type Shift struct {
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start time.Time
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guard int
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sleepEvents []*SleepEvent
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}
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// ParseInput takes the input data and creates a series of "Shift" objects,
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// which are just a structured form of the data.
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func ParseInput(rawData []string) []*Shift {
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sort.Strings(rawData)
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shifts := []*Shift{}
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var currentShift *Shift
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var currentSleepEvent *SleepEvent
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for _, line := range rawData {
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data := strings.Split(line, "]")
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timestamp, _ := time.Parse("2006-01-02 15:04", data[0][1:])
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event := data[1][1:]
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// handle beginning of shift
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if strings.HasPrefix(event, "Guard #") {
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// save old shift first
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if currentShift != nil {
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shifts = append(shifts, currentShift)
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}
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// now extract the guard ID and create a new Shift object
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guardID, _ := strconv.Atoi(strings.Split(event, " ")[1][1:])
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currentShift = &Shift{
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guard: guardID,
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start: timestamp,
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}
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}
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if strings.HasPrefix(event, "falls") {
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currentSleepEvent = &SleepEvent{
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start: timestamp.Minute(),
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}
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}
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if strings.HasPrefix(event, "wakes") {
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currentSleepEvent.end = timestamp.Minute()
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currentShift.sleepEvents = append(currentShift.sleepEvents, currentSleepEvent)
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}
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}
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// save last shift
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shifts = append(shifts, currentShift)
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return shifts
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}
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// BuildGuards takes the shift data created by ParseInput and builds a map of
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// 'guards', with a per-minute counter (and handy sum) of their sleep habits.
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func BuildGuards(data []*Shift) map[int]*Guard {
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guards := make(map[int]*Guard)
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for _, shift := range data {
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// fetch the guard for this shift, initialize if necessary
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var guard *Guard
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// declaring 'ok' here seems to be the only way to keep 'guard' from becoming
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// a local variable inside the conditional. This seems like a flaw.
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var ok bool
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if guard, ok = guards[shift.guard]; !ok {
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guard = &Guard{
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id: shift.guard,
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}
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guards[guard.id] = guard
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}
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for _, event := range shift.sleepEvents {
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guard.sleepTotal += event.end - event.start
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for i := event.start; i < event.end; i++ {
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guard.sleep[i]++
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}
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}
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}
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return guards
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}
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