problem21

Author: TipsyPixie

problem020/problem020.go

@@ -43,13 +43,12 @@ func Run(firstList *linkedList, secondList *linkedList) int {
 		shorterOne, longerOne = firstList, secondList
 	}
 
-	shorterOneCursor, longerOneCursor := shorterOne, longerOne
 	for i := 0; i < lengthDifference; i++ {
-		longerOneCursor = longerOneCursor.next
+		longerOne = longerOne.next
 	}
-	for shorterOneCursor.value != longerOneCursor.value {
-		shorterOneCursor = shorterOneCursor.next
-		longerOneCursor = longerOneCursor.next
+	for shorterOne.value != longerOne.value {
+		shorterOne = shorterOne.next
+		longerOne = longerOne.next
 	}
-	return shorterOneCursor.value
+	return shorterOne.value
 }

problem021/README.md

@@ -0,0 +1,9 @@
+## Daily Coding Problem: Problem #21 [Easy]
+
+Good morning! Here's your coding interview problem for today.
+
+This problem was asked by Snapchat.
+
+Given an array of time intervals (start, end) for classroom lectures (possibly overlapping), find the minimum number of rooms required.
+
+For example, given `[(30, 75), (0, 50), (60, 150)]`, you should return 2.

problem021/problem021.go

@@ -0,0 +1,55 @@
+package problem021
+
+import (
+	"sort"
+)
+
+type Schedule struct {
+	startsAt int
+	endsAt   int
+}
+
+func NewLecture(startsAt int, endsAt int) Schedule {
+	return Schedule{
+		startsAt: startsAt,
+		endsAt:   endsAt,
+	}
+}
+
+const (
+	START = 0
+	END   = 1
+)
+
+type event struct {
+	category int
+	time     int
+}
+
+func Run(lectureSchedules []Schedule) int {
+	events := make([]event, 0, len(lectureSchedules)*2)
+	for _, lectureSchedule := range lectureSchedules {
+		events = append(events,
+			event{
+				category: START,
+				time:     lectureSchedule.startsAt,
+			}, event{
+				category: END,
+				time:     lectureSchedule.endsAt,
+			})
+	}
+	sort.Slice(events, func(i, j int) bool { return events[i].time <= events[j].time })
+
+	classroomCount, maxClassroomCount := 0, 0
+	for _, event := range events {
+		if event.category == START {
+			classroomCount++
+			if classroomCount > maxClassroomCount {
+				maxClassroomCount = classroomCount
+			}
+		} else {
+			classroomCount--
+		}
+	}
+	return maxClassroomCount
+}

problem021/problem021_test.go

@@ -0,0 +1,12 @@
+package problem021
+
+import "testing"
+
+func TestRun(t *testing.T) {
+	lectures := []Schedule{NewLecture(30, 75), NewLecture(0, 50), NewLecture(60, 150)}
+	if Run(lectures) != 2 {
+		t.FailNow()
+	}
+}
+
+//[(30, 75), (0, 50), (60, 150)],