Add task 5 in go

Author: Holger Lösken

src/go/t5/s1.go

@@ -0,0 +1,23 @@
+package main
+
+func Kcomplement(k int, numbers []int) int {
+	pairs := 0
+	occurrencesNumbers := make(map[int]int)
+
+	for _, number := range numbers {
+		if _, ok := occurrencesNumbers[number]; ok {
+			occurrencesNumbers[number]++
+		} else {
+			occurrencesNumbers[number] = 1
+		}
+	}
+
+	for number, occurrence := range occurrencesNumbers {
+		result := k - number
+		if _, ok := occurrencesNumbers[number]; ok {
+			pairs += occurrence * occurrencesNumbers[result]
+		}
+	}
+
+	return pairs
+}

src/go/t5/s1_test.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestKcomplement(t *testing.T) {
+	type Input struct {
+		k int
+		numbers []int
+	}
+
+	type test struct {
+		input Input
+		want int
+	}
+
+	tests := []test {
+		{
+			input: Input {
+				k: 6,
+				numbers: []int { 1, 8, -3, 0, 1, 3, -2, 4, 5 },
+			},
+			want: 7,
+		},
+	}
+
+	for _, tc := range tests {
+		got := Kcomplement(tc.input.k, tc.input.numbers)
+		if !reflect.DeepEqual(tc.want, got) {
+			t.Fatalf("input: %v, expected: %v, got: %v", tc.input, tc.want, got)
+		}
+	}
+}