[2020-12-02] Add solutions for day02

Makefile

@@ -6,6 +6,8 @@ day01:
 	go run main.go day01 input
 
 day02:
+	go run main.go day02 input
+
 day03:
 day04:
 day05:

day02/example.txt

@@ -0,0 +1,3 @@
+1-3 a: abcde
+1-3 b: cdefg
+2-9 c: ccccccccc

day02/parse.go

@@ -0,0 +1,50 @@
+package day02
+
+import (
+	"log"
+	"regexp"
+	"strconv"
+
+	"git.elis.nu/etu/aoc2020/utils"
+)
+
+type PasswordPolicy struct {
+	LowerIndex     int
+	HigherIndex    int
+	ValidationChar byte
+	Password       string
+}
+
+var rows []PasswordPolicy
+
+func ParseFile(input string) {
+	// Parse file
+	for _, line := range utils.GetLinesFromFile("day02/" + input + ".txt") {
+		re := regexp.MustCompile(`(\d+)-(\d+) (\w+): (\w+)`)
+
+		// Match line against regex
+		matches := re.FindStringSubmatch(line)
+
+		// Parse ints
+		index1, err1 := strconv.Atoi(string(matches[1]))
+		index2, err2 := strconv.Atoi(string(matches[2]))
+
+		if err1 != nil {
+			log.Println("Failed to parse entry", err1)
+			continue
+		}
+
+		if err2 != nil {
+			log.Println("Failed to parse entry", err2)
+			continue
+		}
+
+		// Store password policy in list
+		rows = append(rows, PasswordPolicy{
+			LowerIndex:     index1,
+			HigherIndex:    index2,
+			ValidationChar: matches[3][0],
+			Password:       string(matches[4]),
+		})
+	}
+}

day02/solve1.go

@@ -0,0 +1,20 @@
+package day02
+
+import (
+	"log"
+	"strings"
+)
+
+func Solve1() {
+	counter := 0
+
+	for _, row := range rows {
+		occurances := strings.Count(row.Password, string(row.ValidationChar))
+
+		if row.LowerIndex <= occurances && occurances <= row.HigherIndex {
+			counter++
+		}
+	}
+
+	log.Println("2020-12-02.01: Answer:", counter)
+}

day02/solve2.go

@@ -0,0 +1,22 @@
+package day02
+
+import "log"
+
+func Solve2() {
+	counter := 0
+
+	for _, row := range rows {
+		lowerChar := row.Password[row.LowerIndex-1]
+		higherChar := row.Password[row.HigherIndex-1]
+
+		if lowerChar == higherChar {
+			continue
+		}
+
+		if lowerChar == row.ValidationChar || higherChar == row.ValidationChar {
+			counter++
+		}
+	}
+
+	log.Println("2020-12-02.02: Answer:", counter)
+}

main.go

@@ -5,6 +5,7 @@ import (
 	"os"
 
 	"git.elis.nu/etu/aoc2020/day01"
+	"git.elis.nu/etu/aoc2020/day02"
 	"git.elis.nu/etu/aoc2020/utils"
 )
 
@@ -16,5 +17,8 @@ func main() {
 	switch os.Args[1] {
 	case "day01":
 		utils.Perf("2020-12-01", day01.ParseFile, day01.Solve1, day01.Solve2)
+
+	case "day02":
+		utils.Perf("2020-12-02", day02.ParseFile, day02.Solve1, day02.Solve2)
 	}
 }