AdventOfCode2022/11/main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	"time"
)

func mustAtoi(line string) int {
	i, _ := strconv.Atoi(line)
	return i
}

func main() {
	start := time.Now()
	partOne()
	duration := time.Since(start)
	partTwo()
	duration2 := time.Since(start)
	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
}

func makeScanner(test bool) *bufio.Scanner {
	var f *os.File
	if test {
		f, _ = os.Open("inputs/testinput")
	} else {
		f, _ = os.Open("inputs/input")
	}
	reader := bufio.NewReader(f)
	return bufio.NewScanner(reader)
}

type monkey struct {
	items       []int
	operation   string // either "plus", "times", or "square"
	value       int    // ignored for "square"
	test        int    // "divisible by <test>"
	testpass    int    // monkey to throw to if test passes
	testfail    int    // monkey to throw to if test fails
	inspections int
}

func partOne() {
	scanner := makeScanner(false)

	currentMonkey := 0
	monkeys := []monkey{}

	// parse monkeys
	for scanner.Scan() {
		line := scanner.Text()
		switch {
		case strings.HasPrefix(line, "M"):
			currentMonkey = mustAtoi(strings.Trim(line, "Monkey :"))
			monkeys = append(monkeys, monkey{items: make([]int, 0)})
		case strings.HasPrefix(line, "  S"):
			_, after, _ := strings.Cut(line, ":")
			items := strings.Split(after, ",")
			for _, i := range items {
				monkeys[currentMonkey].items = append(monkeys[currentMonkey].items, mustAtoi(strings.TrimSpace(i)))
			}
		case strings.HasPrefix(line, "  O"):
			if strings.Contains(line, "+") {
				monkeys[currentMonkey].operation = "plus"
				l := strings.Split(line, " ")
				monkeys[currentMonkey].value = mustAtoi(l[len(l)-1])
			} else if strings.Contains(line, "old * old") {
				monkeys[currentMonkey].operation = "square"
			} else if strings.Contains(line, "*") {
				monkeys[currentMonkey].operation = "times"
				l := strings.Split(line, " ")
				monkeys[currentMonkey].value = mustAtoi(l[len(l)-1])
			}
		case strings.HasPrefix(line, "  T"):
			l := strings.Split(line, " ")
			monkeys[currentMonkey].test = mustAtoi(l[len(l)-1])
		case strings.HasPrefix(line, "    If t"):
			l := strings.Split(line, " ")
			monkeys[currentMonkey].testpass = mustAtoi(l[len(l)-1])
		case strings.HasPrefix(line, "    If f"):
			l := strings.Split(line, " ")
			monkeys[currentMonkey].testfail = mustAtoi(l[len(l)-1])
		}
	}
	for i := 0; i < 20; i++ {
		for m := range monkeys {
			monkeys[m].inspections += len(monkeys[m].items)
			for _, i := range monkeys[m].items {
				if monkeys[m].operation == "plus" {
					i = (i + monkeys[m].value) / 3
				}
				if monkeys[m].operation == "times" {
					i = (i * monkeys[m].value) / 3
				}
				if monkeys[m].operation == "square" {
					i = (i * i) / 3
				}
				if i%monkeys[m].test == 0 {
					monkeys[monkeys[m].testpass].items = append(monkeys[monkeys[m].testpass].items, i)
				} else {
					monkeys[monkeys[m].testfail].items = append(monkeys[monkeys[m].testfail].items, i)
				}
			}
			monkeys[m].items = []int{}
		}
	}
	one, two := 0, 0
	for _, m := range monkeys {
		if m.inspections > one && m.inspections > two {
			one, two = two, m.inspections
		} else if m.inspections > one {
			one = m.inspections
		}
	}
	fmt.Println(one * two)
}

func partTwo() {
	scanner := makeScanner(false)

	currentMonkey := 0
	monkeys := []monkey{}

	// parse monkeys
	for scanner.Scan() {
		line := scanner.Text()
		switch {
		case strings.HasPrefix(line, "M"):
			currentMonkey = mustAtoi(strings.Trim(line, "Monkey :"))
			monkeys = append(monkeys, monkey{items: make([]int, 0)})
		case strings.HasPrefix(line, "  S"):
			_, after, _ := strings.Cut(line, ":")
			items := strings.Split(after, ",")
			for _, i := range items {
				monkeys[currentMonkey].items = append(
					monkeys[currentMonkey].items, mustAtoi(strings.TrimSpace(i)),
				)
			}
		case strings.HasPrefix(line, "  O"):
			if strings.Contains(line, "+") {
				monkeys[currentMonkey].operation = "plus"
				l := strings.Split(line, " ")
				monkeys[currentMonkey].value = mustAtoi(l[len(l)-1])
			} else if strings.Contains(line, "old * old") {
				monkeys[currentMonkey].operation = "square"
			} else if strings.Contains(line, "*") {
				monkeys[currentMonkey].operation = "times"
				l := strings.Split(line, " ")
				monkeys[currentMonkey].value = mustAtoi(l[len(l)-1])
			}
		case strings.HasPrefix(line, "  T"):
			l := strings.Split(line, " ")
			monkeys[currentMonkey].test = mustAtoi(l[len(l)-1])
		case strings.HasPrefix(line, "    If t"):
			l := strings.Split(line, " ")
			monkeys[currentMonkey].testpass = mustAtoi(l[len(l)-1])
		case strings.HasPrefix(line, "    If f"):
			l := strings.Split(line, " ")
			monkeys[currentMonkey].testfail = mustAtoi(l[len(l)-1])
		}
	}
	common := 1
	for i := range monkeys {
		common = common * monkeys[i].test
	}
	for j := 0; j < 10000; j++ {
		for m := range monkeys {
			monkeys[m].inspections += len(monkeys[m].items)
			for _, i := range monkeys[m].items {
				if monkeys[m].operation == "plus" {
					i = i + monkeys[m].value
				}
				if monkeys[m].operation == "times" {
					i = i * monkeys[m].value
				}
				if monkeys[m].operation == "square" {
					i = i * i
				}
				if i%monkeys[m].test == 0 {
					monkeys[monkeys[m].testpass].items = append(monkeys[monkeys[m].testpass].items, i%common)
				} else {
					monkeys[monkeys[m].testfail].items = append(monkeys[monkeys[m].testfail].items, i%common)
				}
			}
			monkeys[m].items = []int{}
		}
	}
	one, two := 0, 0
	for _, m := range monkeys {
		if m.inspections > one && m.inspections > two {
			one, two = two, m.inspections
		} else if m.inspections > one {
			one = m.inspections
		}
	}
	fmt.Println(one * two)
}