2017-day1: mod to stay in circular array/slice

2017/day01/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/mathutil"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(util.ReadFile("./input.txt"))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(util.ReadFile("./input.txt"))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	digits := parseInput(input)
+	var sum int
+	for i := 0; i < len(digits); i++ {
+		if digits[i] == digits[(i+1)%len(digits)] {
+			sum += digits[i]
+		}
+	}
+	return sum
+}
+
+func part2(input string) int {
+	digits := parseInput(input)
+	var sum int
+	offset := len(digits) / 2
+	for i := 0; i < len(digits); i++ {
+		if digits[i] == digits[(i+offset)%len(digits)] {
+			sum += digits[i]
+		}
+	}
+	return sum
+}
+
+func parseInput(input string) (ans []int) {
+	for _, num := range strings.Split(input, "") {
+		ans = append(ans, mathutil.StrToInt(num))
+	}
+	return ans
+}

2017/day01/main_test.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"example1", "1122", 3},
+		{"example2", "91212129", 9},
+		{"actual", util.ReadFile("input.txt"), 1393},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"example1", "1212", 6},
+		{"example2", "123425", 4},
+		{"actual", util.ReadFile("input.txt"), 1292},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}