+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
+}
\ No newline at end of file