Day 2: Part 1

main.go

@@ -3,10 +3,14 @@ package main
 import (
 	"fmt"
 
-	"github.com/thatguygriff/aoc2020/one"
+	"github.com/thatguygriff/aoc2020/two"
 )
 
 func main() {
-	fmt.Println(one.PartOne())
-	fmt.Println(one.PartTwo())
+	// Day 1
+	// fmt.Println(one.PartOne())
+	// fmt.Println(one.PartTwo())
+
+	// Day 2
+	fmt.Println(two.PartOne())
 }

two/day_two.go

@@ -0,0 +1,90 @@
+package two
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+type passwordPolicy struct {
+	min      int
+	max      int
+	mustHave string
+}
+
+type passwordEntry struct {
+	policy   passwordPolicy
+	password string
+}
+
+type db struct {
+	passwords []passwordEntry
+}
+
+func (d *db) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		var min, max int
+		var mustHave, p string
+
+		count, err := fmt.Sscanf(scanner.Text(), "%d-%d %1s: %s", &min, &max, &mustHave, &p)
+		if err != nil {
+			return err
+		} else if count != 4 {
+			return fmt.Errorf("Unable to parse entry %q", scanner.Text())
+		}
+
+		e := passwordEntry{
+			policy: passwordPolicy{
+				min:      min,
+				max:      max,
+				mustHave: mustHave,
+			},
+			password: p,
+		}
+		d.passwords = append(d.passwords, e)
+	}
+
+	return nil
+}
+
+func validate(password string, policy passwordPolicy) bool {
+	instances := 0
+	for _, letter := range password {
+		if string(letter) == policy.mustHave {
+			instances++
+		}
+	}
+
+	return (instances >= policy.min && instances <= policy.max)
+}
+
+func (d *db) validate() int {
+	valid := 0
+	for _, entry := range d.passwords {
+		if validate(entry.password, entry.policy) {
+			valid++
+		}
+	}
+
+	return valid
+}
+
+// PartOne Find how many passwords are valid according to their policy
+func PartOne() string {
+	database := db{}
+	database.load("two/passwords.txt")
+	valid := database.validate()
+	return fmt.Sprintf("Found %d valid passwords", valid)
+}
+
+// PartTwo
+func PartTwo() string {
+	return ""
+}

two/day_two_test.go

@@ -0,0 +1,28 @@
+package two
+
+import "testing"
+
+func Test_db_load(t *testing.T) {
+	database := db{}
+	if err := database.load("sample.txt"); err != nil {
+		t.Log(err)
+		t.FailNow()
+	}
+
+	if len(database.passwords) != 3 {
+		t.Logf("Expected 3 passwords, Got %d passwords", len(database.passwords))
+		t.FailNow()
+	}
+}
+
+func Test_db_valiate(t *testing.T) {
+	database := db{}
+	database.load("sample.txt")
+
+	validCount := database.validate()
+
+	if validCount != 2 {
+		t.Logf("Expected 2 valid passwords, Got %d valid passwords", validCount)
+		t.FailNow()
+	}
+}

two/sample.txt

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