diff --git a/2015/day03/main.go b/2015/day03/main.go
new file mode 100644
index 0000000..50d7fa5
--- /dev/null
+++ b/2015/day03/main.go
@@ -0,0 +1,71 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"strings"
+
+	"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)
+
+	var ans int
+	if part == 1 {
+		ans = part1(util.ReadFile("./input.txt"))
+	} else {
+		ans = part2(util.ReadFile("./input.txt"))
+	}
+	fmt.Println("Output:", ans)
+}
+
+var dirs = map[string][2]int{
+	"^": [2]int{-1, 0}, // row then col
+	"v": [2]int{1, 0},
+	"<": [2]int{0, -1},
+	">": [2]int{0, 1},
+}
+
+func part1(input string) int {
+	houseCount := map[[2]int]int{[2]int{}: 1}
+	coord := [2]int{0, 0}
+	for _, char := range strings.Split(input, "") {
+		diff := dirs[string(char)]
+		nextCoord := [2]int{
+			coord[0] + diff[0],
+			coord[1] + diff[1],
+		}
+		coord = nextCoord
+		houseCount[coord]++
+	}
+	return len(houseCount)
+}
+
+func part2(input string) int {
+	houseCount := map[[2]int]int{[2]int{}: 2}
+	santaCoord := [2]int{0, 0}
+	robotCoord := [2]int{0, 0}
+	for i, char := range strings.Split(input, "") {
+		diff := dirs[string(char)]
+		if i%2 == 0 {
+			nextSantaCoord := [2]int{
+				santaCoord[0] + diff[0],
+				santaCoord[1] + diff[1],
+			}
+			santaCoord = nextSantaCoord
+			houseCount[santaCoord]++
+		} else {
+			nextRobotCoord := [2]int{
+				robotCoord[0] + diff[0],
+				robotCoord[1] + diff[1],
+			}
+			robotCoord = nextRobotCoord
+			houseCount[robotCoord]++
+		}
+	}
+	return len(houseCount)
+}
diff --git a/2015/day03/main_test.go b/2015/day03/main_test.go
new file mode 100644
index 0000000..e6daafd
--- /dev/null
+++ b/2015/day03/main_test.go
@@ -0,0 +1,41 @@
+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
+	}{
+		{"actual", util.ReadFile("input.txt"), 2565},
+	}
+	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
+	}{
+		{"actual", util.ReadFile("input.txt"), 2639},
+	}
+	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)
+			}
+		})
+	}
+}