Day 7 solution

I will probably end up regretting this since I assume the "wait to be given an input from some other process before continuing execution" paradigm is going to come up again, but this part 2 goroutine+channel solution felt good (taking advantage of Go features) and made me happy, so I rolled with it.

utilities/permutations.go

@@ -0,0 +1,34 @@
+package utilities
+
+type Permutable interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 | ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64
+}
+
+func GetPermutations[T Permutable](arr []T) [][]T {
+	var helper func([]T, int)
+	res := [][]T{}
+
+	helper = func(arr []T, n int) {
+		if n == 1 {
+			tmp := make([]T, len(arr))
+			copy(tmp, arr)
+			res = append(res, tmp)
+		} else {
+			for i := 0; i < n; i++ {
+				helper(arr, n-1)
+				if n%2 == 1 {
+					tmp := arr[i]
+					arr[i] = arr[n-1]
+					arr[n-1] = tmp
+				} else {
+					tmp := arr[0]
+					arr[0] = arr[n-1]
+					arr[n-1] = tmp
+				}
+			}
+		}
+	}
+
+	helper(arr, len(arr))
+	return res
+}