Day 9.1 solution.

2018/internal/day09/game.go

@@ -0,0 +1,39 @@
+package day09
+
+// Returns the winning player's index and score
+func PlayGame(numPlayers, finNum int) (int, int) {
+	players := make([]int, numPlayers)
+
+	// initialize the 'board'
+	currentMarble := &Marble{Number: 0}
+	currentMarble.CW = currentMarble
+	currentMarble.CCW = currentMarble
+
+	currentPlayer := 0
+	for i := 1; currentMarble.Number < finNum; i++ {
+		var score int
+		currentMarble, score = currentMarble.PlaceNewMarble(i)
+		players[currentPlayer] += score
+
+		currentPlayer++
+		if currentPlayer >= len(players) {
+			currentPlayer = 0
+		}
+	}
+
+	return findWinnerData(players)
+}
+
+func findWinnerData(players []int) (int, int) {
+	topScore := -1
+	winner := -1
+
+	for player, score := range players {
+		if score > topScore {
+			topScore = score
+			winner = player
+		}
+	}
+
+	return winner, topScore
+}