Add day 6 solution.

2020/day06.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/util"
+)
+
+func countAnswerUnion(input string) int {
+	charMap := make(map[rune]bool)
+
+	for _, char := range input {
+		if char == ' ' {
+			continue
+		}
+
+		if _, ok := charMap[char]; !ok {
+			charMap[char] = true
+		}
+	}
+	return len(charMap)
+}
+
+func countAnswerIntersection(input string) int {
+	charMap := make(map[rune]int)
+	answers := strings.Split(strings.Trim(input, " "), " ")
+
+	for _, answer := range answers {
+		for _, char := range answer {
+			charMap[char]++
+		}
+	}
+
+	total := 0
+	for _, count := range charMap {
+		if count == len(answers) {
+			total++
+		}
+	}
+	return total
+}
+
+func main() {
+	step := os.Args[1]
+	values := fileutils.InputParserStrings(os.Args[2])
+	groups := util.SplitOnBlankLine(values)
+
+	total := 0
+	for _, line := range groups {
+		if step == "1" {
+			total += countAnswerUnion(line)
+		}
+		if step == "2" {
+			total += countAnswerIntersection(line)
+		}
+	}
+	fmt.Println("Total:", total)
+}