AdventOfCode2023/02/main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"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 game struct {
	red   int
	green int
	blue  int
}

func parseRound(line string) game {
	g := game{}
	n := []byte{}
	for i := 0; i < len(line); i++ {
		switch line[i] {
		case ' ':
			continue
		case ',':
			i++
			continue
		case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0':
			n = append(n, line[i])
		case 'r':
			g.red = mustAtoi(string(n))
			n = []byte{}
			i += 4
		case 'g':
			g.green = mustAtoi(string(n))
			n = []byte{}
			i += 6
		case 'b':
			g.blue = mustAtoi(string(n))
			n = []byte{}
			i += 5
		}
	}
	return g
}

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

	sum := 0
	round := 0
	max := game{
		red:   12,
		green: 13,
		blue:  14,
	}
	for scanner.Scan() {
		line := scanner.Text()
		ok := true
		round++
		for i, c := range line {
			if c == ':' {
				line = line[i+2:]
				break
			}
		}
		var start, end int
		for i, c := range line {
			if c == ';' || i == len(line)-1 {
				end = i + 1
				g := parseRound(line[start:end])
				if g.red > max.red || g.blue > max.blue || g.green > max.green {
					ok = false
				}
				start = i + 2
			}
		}
		if ok {
			sum += round
		}
	}
	fmt.Println(sum)
}

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

	sum := 0
	for scanner.Scan() {
		line := scanner.Text()
		for i, c := range line {
			if c == ':' {
				line = line[i+2:]
				break
			}
		}
		max := game{}
		var start, end int
		for i, c := range line {
			if c == ';' || i == len(line)-1 {
				end = i + 1
				g := parseRound(line[start:end])
				if g.red > max.red {
					max.red = g.red
				}
				if g.blue > max.blue {
					max.blue = g.blue
				}
				if g.green > max.green {
					max.green = g.green
				}
				start = i + 2
			}
		}
		sum += max.blue * max.green * max.red
	}
	fmt.Println(sum)
}