Improve things in main.go

diffsect.go

@@ -0,0 +1,28 @@
+package main
+
+// diffsect removes all items in `a` from `b`, then removes all items from `b`
+// which are not in `c`. Effectively: intersect(difference(b, a), c)
+func diffsect(a, b, c *[]string) *[]string {
+	result := []string{}
+	mapA := map[string]bool{}
+	mapC := map[string]bool{}
+
+	for _, x := range *a {
+		mapA[x] = true
+	}
+
+	for _, x := range *c {
+		mapC[x] = true
+	}
+
+	for _, x := range *b {
+		_, okA := mapA[x]
+		_, okC := mapC[x]
+
+		if !okA && okC {
+			result = append(result, x)
+		}
+	}
+
+	return &result
+}