From 141bc3098ca086b43834b637eb57db5f56625304 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Krejczinger=20=C3=81rp=C3=A1d?=
 <krejczinger.arpad@gmail.com>
Date: Mon, 16 Mar 2026 00:38:21 +0100
Subject: [PATCH] SumAllTails implemented, refactor tests

---
 arrays/sum.go      | 15 +++++++++++++++
 arrays/sum_test.go | 21 +++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/arrays/sum.go b/arrays/sum.go
index 2c94226..7a82a57 100644
--- a/arrays/sum.go
+++ b/arrays/sum.go
@@ -18,3 +18,18 @@ func SumAll(numbersToSum ...[]int) []int {
 
 	return sums
 }
+
+func SumAllTails(numbersToSum ...[]int) []int {
+	var sums []int
+
+	for _, numbers := range numbersToSum {
+		if len(numbers) == 0 {
+			sums = append(sums, 0)
+		} else {
+			tail := numbers[1:]
+			sums = append(sums, Sum(tail))
+		}
+	}
+
+	return sums
+}
diff --git a/arrays/sum_test.go b/arrays/sum_test.go
index 8640a9e..4774892 100644
--- a/arrays/sum_test.go
+++ b/arrays/sum_test.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"reflect"
 	"slices"
 	"testing"
 )
@@ -37,3 +38,23 @@ func TestSumAll(t *testing.T) {
 		t.Errorf("got %d want %v", got, want)
 	}
 }
+
+func TestSumAllTails(t *testing.T) {
+	checkSums := func(t testing.TB, got, want []int) {
+		t.Helper()
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("got %v want %v", got, want)
+		}
+	}
+
+	t.Run("sums of slices", func(t *testing.T) {
+		got := SumAllTails([]int{1, 2}, []int{0, 9})
+		want := []int{2, 9}
+		checkSums(t, got, want)
+	})
+	t.Run("sums with some empty slices", func(t *testing.T) {
+		got := SumAllTails([]int{}, []int{3, 4, 5})
+		want := []int{0, 9}
+		checkSums(t, got, want)
+	})
+}