day04

2018/day04/part1/main.go

@@ -0,0 +1,112 @@
+package main
+
+import (
+	"adventofcode/util"
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	input := util.ReadFile("../input.txt")
+	lines := strings.Split(input, "\n")
+
+	// sort inputs by time stamp, string sorting is sufficient
+	sort.Strings(lines)
+
+	timeEntries := make([]entry, len(lines))
+	for i, line := range lines {
+		timeEntries[i] = makeEntry(line)
+	}
+
+	// find which guard has slept the most total time
+	// then find which minute he is asleep at most frequently
+	mapIDGuard := make(map[int]*guard)
+	lastGuardID := timeEntries[0].ID
+	for i, timeEntry := range timeEntries {
+		if timeEntry.ID != 0 {
+			lastGuardID = timeEntry.ID
+		} else {
+			// if the time entry is awake, then check the next one entry
+			// if the next entry is the same day, then assume its the same guard
+			// update that guard's stats
+			if !timeEntry.awake && i+1 != len(timeEntries) &&
+				timeEntries[i+1].day == timeEntry.day {
+				endTime := timeEntries[i+1].minute
+				startTime := timeEntry.minute
+				if mapIDGuard[lastGuardID] == nil {
+					mapIDGuard[lastGuardID] = &guard{}
+				}
+				mapIDGuard[lastGuardID].totalTimeAsleep += endTime - startTime
+				for startTime < endTime {
+					mapIDGuard[lastGuardID].minutesAsleep[startTime]++
+					startTime++
+				}
+			}
+		}
+	}
+
+	// who sleeps the most
+	var IDOfSleepiestGuard, bestMinute, highestFreq int
+	for i, g := range mapIDGuard {
+		if IDOfSleepiestGuard == 0 {
+			IDOfSleepiestGuard = i
+		}
+		if g.totalTimeAsleep > mapIDGuard[IDOfSleepiestGuard].totalTimeAsleep {
+			IDOfSleepiestGuard = i
+		}
+	}
+
+	// find the minute they are the asleep the most
+	for min, freq := range mapIDGuard[IDOfSleepiestGuard].minutesAsleep {
+		if freq > highestFreq {
+			bestMinute = min
+			highestFreq = freq
+		}
+	}
+
+	// print ID * time (minute)
+	fmt.Printf("Sleepiest guard is %v, at minute %v.\nAoC answer: %v\n",
+		IDOfSleepiestGuard,
+		bestMinute,
+		IDOfSleepiestGuard*bestMinute,
+	)
+}
+
+type entry struct {
+	ID, year, month, day, minute int
+	awake                        bool
+}
+
+func makeEntry(line string) entry {
+	fmt.Println(line)
+	var e entry
+	e.year, _ = strconv.Atoi(line[1:5])
+	e.month, _ = strconv.Atoi(line[6:8])
+	e.day, _ = strconv.Atoi(line[9:11])
+
+	hour, _ := strconv.Atoi(line[12:14])
+	// if started before midnight, zero out minute value
+	if hour != 0 {
+		e.minute = 0
+	} else {
+		e.minute, _ = strconv.Atoi(line[15:17])
+	}
+
+	// if the instruction is that the guard has fallen asleep, leave awake=false
+	if strings.Contains(line, "falls asleep") {
+		return e
+	}
+
+	e.awake = true
+	if strings.Contains(line, "Guard") {
+		e.ID, _ = strconv.Atoi(line[strings.Index(line, "#")+1 : strings.Index(line, " begins")])
+	}
+	return e
+}
+
+type guard struct {
+	totalTimeAsleep int
+	minutesAsleep   [60]int
+}