Add solution for "Roller Coaster"

README.md

@@ -7,9 +7,11 @@ Just one thing: **Don't just copy them.** Take the puzzle yourself and afterward
 ## Finished puzzles
 
 - Medium
+  - [Bender - Episode 1](https://www.codingame.com/training/medium/bender-episode-1)
   - [Don't Panic - Episode 1](https://www.codingame.com/training/medium/don't-panic-episode-1)
   - [Shadows of the Knight - Episode 1](https://www.codingame.com/training/medium/shadows-of-the-knight-episode-1)
-  - [Bender - Episode 1](https://www.codingame.com/training/medium/bender-episode-1)
   - [There is no Spoon - Episode 1](https://www.codingame.com/training/medium/there-is-no-spoon-episode-1)
+- Hard
+  - [Roller Coaster](https://www.codingame.com/training/hard/roller-coaster)
 - Community
   - [Texas Holdem](https://www.codingame.com/training/community/texas-holdem) by AdamHill

finished/hard_roller-coaster.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"time"
+)
+
+type calculationResult struct{ Seated, Next int }
+
+var (
+	groups           [1000]int
+	calculationCache = map[int]calculationResult{}
+)
+
+func main() {
+	defer timeTrack(time.Now(), "main")
+	scanner := bufio.NewScanner(os.Stdin)
+	scanner.Buffer(make([]byte, 1000000), 1000000)
+	scanner.Split(bufio.ScanWords)
+
+	var L, C, N, i int
+	scanner.Scan()
+	L = toInt(scanner.Bytes())
+	scanner.Scan()
+	C = toInt(scanner.Bytes())
+	scanner.Scan()
+	N = toInt(scanner.Bytes())
+
+	log.Printf("C: %d", C)
+
+	for ; i < N; i++ {
+		scanner.Scan()
+		groups[i] = toInt(scanner.Bytes())
+	}
+
+	var earned, next, seated, j int
+	for i = 0; i < C; i++ {
+		key := next
+		seated = 0
+
+		if cr, ok := calculationCache[key]; ok {
+			seated = cr.Seated
+			next = cr.Next
+		} else {
+			j = 0
+			for j < N && groups[next] <= L-seated {
+				seated += groups[next]
+				j++
+				next++
+				if next == N {
+					next = 0
+				}
+			}
+			calculationCache[key] = calculationResult{Seated: seated, Next: next}
+		}
+
+		earned += seated
+	}
+
+	fmt.Printf("%d\n", earned)
+}
+
+func toInt(buf []byte) (n int) {
+	for _, v := range buf {
+		n = n*10 + int(v-'0')
+	}
+	return
+}
+
+func timeTrack(start time.Time, name string) {
+	elapsed := time.Since(start)
+	log.Printf("%s took %s", name, elapsed)
+}