feat: three sum

pkg/three_sum/main.go

@@ -0,0 +1,41 @@
+package three_sum
+
+import (
+	"slices"
+)
+
+func TwoSum(numbers []int, target int, solutions map[[3]int]bool) {
+	start := 0
+	end := len(numbers) - 1
+
+	for start < end {
+		sum := numbers[start] + numbers[end]
+
+		if sum < target {
+			start++
+		} else if sum > target {
+			end--
+		} else {
+			solutions[[3]int{-target, numbers[start], numbers[end]}] = true
+			start++
+		}
+	}
+}
+
+func ThreeSum(nums []int) [][]int {
+	slices.Sort(nums)
+
+	solutions := map[[3]int]bool{}
+
+	for i := range nums {
+		TwoSum(nums[i+1:], -nums[i], solutions)
+	}
+
+	result := [][]int{}
+
+	for solution := range solutions {
+		result = append(result, solution[:])
+	}
+
+	return result
+}

pkg/three_sum/main_test.go

@@ -0,0 +1,26 @@
+package three_sum_test
+
+import (
+	"testing"
+
+	"git.maximhutz.com/practice/pkg/three_sum"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test1(t *testing.T) {
+	assert.ElementsMatch(t,
+		[][]int{{-1, -1, 2}, {-1, 0, 1}},
+		three_sum.ThreeSum([]int{-1, 0, 1, 2, -1, -4}))
+}
+
+func Test2(t *testing.T) {
+	assert.Equal(t,
+		[][]int{},
+		three_sum.ThreeSum([]int{0, 1, 1}))
+}
+
+func Test3(t *testing.T) {
+	assert.Equal(t,
+		[][]int{{0, 0, 0}},
+		three_sum.ThreeSum([]int{0, 0, 0}))
+}