Day 12 solution

Okay, I had to seek some advice on this one. The orbital period + least-common-multiple solution was not coming to me naturally.

utilities/math.go

@@ -0,0 +1,27 @@
+package utilities
+
+func GCD[T Integer](a, b T) T {
+	if b == 0 {
+		return a
+	}
+	return GCD(b, a%b)
+}
+
+func LCM[T Integer](nums ...T) uint64 {
+	num := len(nums)
+	if num == 0 {
+		return 0
+	} else if num == 1 {
+		return uint64(nums[0])
+	}
+
+	ret := lcm(nums[0], nums[1])
+	for i := 2; i < len(nums); i++ {
+		ret = lcm(uint64(nums[i]), ret)
+	}
+	return ret
+}
+
+func lcm[T Integer](a, b T) uint64 {
+	return uint64(a*b) / uint64(GCD(a, b))
+}

utilities/vector.go

@@ -7,6 +7,12 @@ type Vec2[T Number] struct {
 	Y T
 }
 
+type Vec3[T Number] struct {
+	X T
+	Y T
+	Z T
+}
+
 func (v Vec2[T]) Dot(other Vec2[T]) T {
 	return (v.X * other.X) + (v.Y * other.Y)
 }
@@ -37,3 +43,27 @@ func VecBetween[T Number](a, b Vec2[T]) Vec2[T] {
 		Y: a.Y - b.Y,
 	}
 }
+
+func (v Vec3[T]) Dot(other Vec3[T]) T {
+	return (v.X * other.X) + (v.Y * other.Y) + (v.Z * other.Z)
+}
+
+func (v Vec3[T]) Len() T {
+	return T(math.Sqrt(float64(v.LenSquared())))
+}
+
+func (v Vec3[T]) LenSquared() T {
+	return (v.X * v.X) + (v.Y * v.Y) + (v.Z * v.Z)
+}
+
+func (v *Vec3[T]) Add(other Vec3[T]) {
+	v.X += other.X
+	v.Y += other.Y
+	v.Z += other.Z
+}
+
+func (v Vec3[T]) Equals(other Vec3[T]) bool {
+	return v.X == other.X &&
+		v.Y == other.Y &&
+		v.Z == other.Z
+}