AoC 2020: day4

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

2018-go/day_09/main.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+)
+
+type marble struct {
+	left  *marble
+	right *marble
+	value uint64
+}
+
+func (m *marble) placeMarble(newMarbleValue uint64) *marble {
+	var newMarble = marble{left: m.right, right: m.right.right, value: newMarbleValue}
+
+	m.right.right.left = &newMarble
+	m.right.right = &newMarble
+
+	return &newMarble
+}
+
+func (m *marble) removeCurrentMarble() (*marble, uint64) {
+	val := m.value
+
+	m.left.right = m.right
+	m.right.left = m.left
+
+	return m.right, val
+}
+
+func (m *marble) changeCurrentMarble(clockwiseMove int) *marble {
+	var newCurrentMarble = m
+	if clockwiseMove > 0 {
+		for i := 0; i < clockwiseMove; i++ {
+			newCurrentMarble = newCurrentMarble.right
+		}
+	} else {
+		for i := 0; i > clockwiseMove; i-- {
+			newCurrentMarble = newCurrentMarble.left
+		}
+	}
+	return newCurrentMarble
+}
+
+func main() {
+	var elfs, currentElf int
+	var currentMarbleValue, lastMarbleValue, maxPoint uint64
+	var currentMarble = &marble{left: nil, right: nil, value: 0}
+	elfsPoint := make(map[int]uint64)
+
+	file, err := os.Open("./input")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	scan := bufio.NewScanner(file)
+	scan.Scan()
+	line := scan.Text()
+	fmt.Sscanf(line, "%d players; last marble is worth %d points", &elfs, &lastMarbleValue)
+
+	//Part Two: uncomment next line
+	//lastMarbleValue *= 100
+
+	for i := 0; i < elfs; i++ {
+		elfsPoint[i] = 0
+	}
+
+	currentMarble.left = currentMarble
+	currentMarble.right = currentMarble
+
+	for currentMarbleValue < lastMarbleValue {
+		currentMarbleValue++
+		if currentMarbleValue%23 == 0 {
+			var val uint64
+			currentMarble = currentMarble.changeCurrentMarble(-7)
+			currentMarble, val = currentMarble.removeCurrentMarble()
+			elfsPoint[currentElf] += (currentMarbleValue + val)
+			if elfsPoint[currentElf] > maxPoint {
+				maxPoint = elfsPoint[currentElf]
+			}
+		} else {
+			currentMarble = currentMarble.placeMarble(currentMarbleValue)
+		}
+		currentElf = (currentElf + 1) % elfs
+	}
+
+	fmt.Printf("Part One/Two: %v\n", maxPoint)
+
+}