AdventOfCode2023/04/main.go

package main

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

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

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

	sum := 0
	for scanner.Scan() {
		line := scanner.Text()
		draws := map[int]struct{}{}
		state := 0
		acc := []rune{}
		score := 0
		for _, c := range line {
			// slice off the 'game :' part
			if state == 0 {
				if c == ':' {
					state = 1
				}
				continue
			}
			switch c {
			case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
				acc = append(acc, c)
			case '|':
				state = 2
				acc = []rune{}
			case ' ':
				if len(acc) != 0 && state == 1 {
					draws[mustAtoi(acc)] = struct{}{}
				} else if state == 2 {
					if _, ok := draws[mustAtoi(acc)]; ok {
						if score == 0 {
							score = 1
						} else {
							score *= 2
						}
					}
				}
				acc = []rune{}
			}
		}
		if _, ok := draws[mustAtoi(acc)]; ok {
			if score == 0 {
				score = 1
			} else {
				score *= 2
			}
		}
		sum += score
	}
	fmt.Println(sum)
}

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

	card := 1
	dupes := map[int]int{}
	sum := 0
	for scanner.Scan() {
		line := scanner.Text()
		draws := map[int]struct{}{}
		state := 0
		acc := []rune{}
		score := 0
		dupes[card]++
		for _, c := range line {
			// slice off the 'game :' part
			if state == 0 {
				if c == ':' {
					state = 1
				}
				continue
			}
			switch c {
			case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
				acc = append(acc, c)
			case '|':
				state = 2
				acc = []rune{}
			case ' ':
				if len(acc) != 0 && state == 1 {
					draws[mustAtoi(acc)] = struct{}{}
				} else if state == 2 {
					if _, ok := draws[mustAtoi(acc)]; ok {
						score++
					}
				}
				acc = []rune{}
			}
		}
		if _, ok := draws[mustAtoi(acc)]; ok {
			score++
		}
		for i := card + 1; i <= card+score; i++ {
			dupes[i] += dupes[card]
		}
		sum += dupes[card]
		card++
	}
	fmt.Println(sum)
}