day11

2022/go/day11/day11.go

@@ -0,0 +1,148 @@
+package day11
+
+import (
+	_ "fmt"
+	"strings"
+	"sort"
+	"adventofcode2022/utils"
+	"math/big"
+)
+
+type op int
+
+const (
+	addition op = iota + 1
+	multiply
+	square
+)
+
+type monkey struct {
+	items []*big.Int
+	operation op
+	opArg *big.Int
+	test *big.Int
+	ifTrue int
+	ifFalse int
+	inspected int
+}
+
+func Part1(input string) int {
+
+	monkeys := parseInput(input)
+	var level = big.NewInt(0)
+	for round := 0; round < 20; round++ {
+		for i, monkey := range monkeys {
+			for _, item := range monkey.items {
+				monkeys[i].inspected++
+				switch monkey.operation {
+				case addition:
+					level = new(big.Int).Add(item, monkey.opArg)
+				case multiply:
+					level = new(big.Int).Mul(item, monkey.opArg)
+				case square:
+					level = new(big.Int).Mul(item, item)
+				}
+				level = new(big.Int).Div(level, big.NewInt(3))
+				t := &big.Int{}
+				t.Mod(level, monkey.test)
+				if t.Sign() == 0 {
+					monkeys[monkey.ifTrue].items = append(monkeys[monkey.ifTrue].items, level)
+				} else {
+					monkeys[monkey.ifFalse].items = append(monkeys[monkey.ifFalse].items, level)
+				}
+				
+			}
+			monkeys[i].items = monkeys[i].items[:0]
+		}
+	}
+	sort.Slice(monkeys, func(i, j int) bool {
+		return monkeys[i].inspected > monkeys[j].inspected
+	})
+	
+	return  monkeys[0].inspected * monkeys[1].inspected
+}
+
+func Part2(input string) int {
+	monkeys := parseInput(input)
+	var level = big.NewInt(0)
+	commonDivisor := big.NewInt(3 * 13 * 19 * 17 * 5 * 7 * 11 * 2)
+	for round := 0; round < 10000; round++ {
+		for i, monkey := range monkeys {
+			for _, item := range monkey.items {
+				monkeys[i].inspected++
+				switch monkey.operation {
+				case addition:
+					level = new(big.Int).Add(item, monkey.opArg)
+				case multiply:
+					level = new(big.Int).Mul(item, monkey.opArg)
+				case square:
+					level = new(big.Int).Mul(item, item)
+				}
+				level = level.Mod(level, commonDivisor)
+				t := &big.Int{}
+				t.Mod(level, monkey.test)
+				if t.Sign() == 0 {
+					monkeys[monkey.ifTrue].items = append(monkeys[monkey.ifTrue].items, level)
+				} else {
+					monkeys[monkey.ifFalse].items = append(monkeys[monkey.ifFalse].items, level)
+				}
+				
+			}
+			monkeys[i].items = monkeys[i].items[:0]
+		}
+	}
+	sort.Slice(monkeys, func(i, j int) bool {
+		return monkeys[i].inspected > monkeys[j].inspected
+	})
+	
+	return  monkeys[0].inspected * monkeys[1].inspected
+}
+
+func parseInput(input string) []monkey {
+	monkeys := []monkey{}
+
+	for i, monkeyString := range strings.Split(input, "\n\n") {
+		for _, line := range strings.Split(monkeyString, "\n") {
+			if strings.HasPrefix(line, "Monkey") {
+				monkeys = append(monkeys, monkey{})
+			} else if strings.HasPrefix(line, "  Starting items: ") {
+				s := strings.TrimPrefix(line, "  Starting items: ")
+				for _, piece := range strings.Split(s, ", ") {
+					t := utils.MustAtoi(piece)
+					monkeys[i].items =  append(monkeys[i].items, big.NewInt(int64(t)))
+				}
+			} else if strings.HasPrefix(line, "  Operation: new = ") {
+				s := strings.TrimPrefix(line, "  Operation: new = ")
+				if strings.HasPrefix(s, "old + ") {
+					s2 := strings.TrimPrefix(s, "old + ")
+					monkeys[i].operation = addition
+					t := utils.MustAtoi(s2)
+					monkeys[i].opArg = big.NewInt(int64(t))
+				} else if s == "old * old" {
+					monkeys[i].operation = square
+				} else if strings.HasPrefix(s, "old * ") {
+					s2 := strings.TrimPrefix(s, "old * ")
+					monkeys[i].operation = multiply
+					t := utils.MustAtoi(s2)
+					monkeys[i].opArg = big.NewInt(int64(t))
+				}
+
+			} else if strings.HasPrefix(line, "  Test: divisible by ") {
+				s := strings.TrimPrefix(line, "  Test: divisible by ")
+				t := utils.MustAtoi(s)
+				monkeys[i].test = big.NewInt(int64(t))
+			} else if strings.HasPrefix(line, "    If true: throw to monkey ") {
+				s := strings.TrimPrefix(line, "    If true: throw to monkey ")
+				monkeys[i].ifTrue = utils.MustAtoi(s)
+			} else if strings.HasPrefix(line, "    If false: throw to monkey ") {
+				s := strings.TrimPrefix(line, "    If false: throw to monkey ")
+				monkeys[i].ifFalse = utils.MustAtoi(s)
+			} else if line == "" {
+				// do nothing
+			} else {
+				panic("unknown input")
+			}
+		}
+	}
+	return monkeys
+}