AdventOfCode2020/06/main.go

package main

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

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 union(s string) string {
	result := ""

	for _, r := range s {
		if !strings.ContainsRune(result, r) {
			result = result + string(r)
		}
	}

	return result
}

func intersection(s, q string) string {
	result := ""

	for _, r := range s {
		if strings.ContainsRune(q, r) {
			result = result + string(r)
		}
	}

	return result
}

// For each of the people in their group, you write down the questions for which they answer "yes", one per line. For example:
// abcx
// abcy
// abcz
// In this group, there are 6 questions to which anyone answered "yes": a, b, c, x, y, and z.
// (Duplicate answers to the same question don't count extra; each question counts at most once.)
// Another group asks for your help, then another, and eventually you've collected answers from every group on the plane (your puzzle input).
// Each group's answers are separated by a blank line, and within each group, each person's answers are on a single line.

func partOne() {
	f, _ := os.Open("input")
	reader := bufio.NewReader(f)
	scanner := bufio.NewScanner(reader)

	sum := 0
	currentForm := ""

	for scanner.Scan() {
		line := scanner.Text()
		if line == "" {
			sum = sum + len(union(currentForm))
			currentForm = ""
		} else {
			currentForm = currentForm + line
		}
	}
	sum = sum + len(union(currentForm))

	fmt.Println(sum)
}

// As you finish the last group's customs declaration, you notice that you misread one word in the instructions:
// You don't need to identify the questions to which anyone answered "yes";
// you need to identify the questions to which everyone answered "yes"!

func partTwo() {
	f, _ := os.Open("input")
	reader := bufio.NewReader(f)
	scanner := bufio.NewScanner(reader)

	sum := 0
	var currentForm string
	newgroup := true

	for scanner.Scan() {
		line := scanner.Text()
		if newgroup {
			currentForm = line
			newgroup = false
		} else {
			if line != "" {
				currentForm = intersection(currentForm, line)
			} else {
				sum = sum + len(currentForm)
				newgroup = true
			}
		}
	}
	sum = sum + len(currentForm)

	fmt.Println(sum)
}