#28. Add ArrayIntersect + test

README.md

@@ -211,4 +211,11 @@ pgo.ArrayKeys(map[string]int{"foo": 1, "bar": 8, "fizz": 12, "baz": 0}) // []str
 pgo.ArrayKeys(map[interface{}]int{3.45: 32, "foo": 33, 8: 53, "bar": 1, 9: 1}) // []interface{}{3.45, "foo", 8, "bar", 9}
 ```
 
+#### ArrayIntersect
+computes the intersection of arrays
+```go
+pgo.ArrayIntersect([]int{12, 54, 32, 12, 33}, []int{3, 12, 54, 9}, []int{12, 33, 9}) // []int{12, 54}
+
+pgo.ArrayIntersect([]string{"foo", "bar", "baz", "fizz", "bazz", "fizz", "fizz"}, []string{"bar", "fizz"}, []string{"foo", "bar", "hey"}) // []string{"foo", "bar", "fizz"}
+```
 See more examples in *_test.go files.

array.go

@@ -178,3 +178,42 @@ func getFloat(unk interface{}) (float64, error) {
 	fv := v.Convert(floatType)
 	return fv.Float(), nil
 }
+
+// ArrayIntersect computes the intersection of arrays
+func ArrayIntersect(arrays ...interface{}) []interface{} {
+	s := reflect.ValueOf(arrays[0])
+	len := s.Len()
+
+	var result []interface{}
+	isFound := false
+
+	intersected := make(map[interface{}]bool)
+	for i := 0; i < len; i++ {
+		needle := s.Index(i).Interface()
+
+		for _, v := range arrays[1:] {
+			switch reflect.TypeOf(v).Kind() {
+			case reflect.Slice:
+				ss := reflect.ValueOf(v)
+				sLen := ss.Len()
+
+				for j := 0; j < sLen; j++ {
+					if needle == ss.Index(j).Interface() && !intersected[needle] {
+						isFound = true
+						intersected[needle] = true // del op is more expensive for slices
+						goto out                   // it is stupid to iterate O(n^2) if found
+					}
+				}
+			}
+		}
+
+	out:
+		if isFound {
+			result = append(result, needle)
+		}
+
+		isFound = false
+	}
+
+	return result
+}

array_test.go

@@ -249,3 +249,31 @@ func TestArraySum(t *testing.T) {
 		}
 	}
 }
+
+var testArrayIntersect = []struct {
+	values interface{}
+	diff   interface{}
+	diff2  interface{}
+	result interface{}
+}{
+	{[]int{12, 54, 32, 12, 33}, []int{3, 12, 54, 9}, []int{12, 33, 9}, []int{12, 54}},
+	{[]string{"foo", "bar", "baz", "fizz", "bazz", "fizz", "fizz"}, []string{"bar", "fizz"},
+		[]string{"foo", "bar", "hey"}, []string{"foo", "bar", "fizz"}},
+}
+
+func TestArrayIntersect(t *testing.T) {
+	for _, object := range testArrayIntersect {
+		res := pgo.ArrayIntersect(object.values, object.diff, object.diff2)
+
+		resVal := reflect.ValueOf(object.result)
+		resLen := resVal.Len()
+
+		s := reflect.ValueOf(object.result)
+
+		for i := 0; i < resLen; i++ {
+			if resVal.Index(i).Interface() != s.Index(i).Interface() {
+				t.Fatalf("want %v, got %v", s.Index(i).Interface(), res[i])
+			}
+		}
+	}
+}