From c9d013416792e70aae5289ccba989bb9c0d8788e Mon Sep 17 00:00:00 2001
From: dillon <dillonstreator@gmail.com>
Date: Sun, 5 Jun 2022 22:17:27 -0500
Subject: [PATCH 1/3] initial interleave working

---
 README.md     | 10 ++++++++++
 slice.go      | 41 +++++++++++++++++++++++++++++++++++++++++
 slice_test.go | 42 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+)

diff --git a/README.md b/README.md
index dc3fee1d..ac15afb3 100644
--- a/README.md
+++ b/README.md
@@ -84,6 +84,7 @@ Supported helpers for slices:
 - Reject
 - Count
 - CountBy
+- Interleave
 
 Supported helpers for maps:
 
@@ -596,6 +597,15 @@ count := lo.CountBy[int]([]int{1, 5, 1}, func(i int) bool {
 // 2
 ```
 
+### Interleave
+
+Round-robbin alternating input slices and sequentially appending value at index into result.
+
+```go
+interleaved := lo.Interleave[int]([]int{1, 4, 7}, []int{2, 5, 8}, []int{3, 6, 9})
+// []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+```
+
 ### Subset
 
 Return part of a slice.
diff --git a/slice.go b/slice.go
index 1fb781b1..51c8337c 100644
--- a/slice.go
+++ b/slice.go
@@ -406,3 +406,44 @@ func Replace[T comparable](collection []T, old T, new T, n int) []T {
 func ReplaceAll[T comparable](collection []T, old T, new T) []T {
 	return Replace(collection, old, new, -1)
 }
+
+// Interleave round-robbin alternating input slices and sequentially appending value at index into result
+func Interleave[T any](collections ...[]T) []T {
+	if len(collections) == 0 {
+		return []T{}
+	}
+
+	if len(collections) == 1 {
+		return collections[0]
+	}
+
+	maxSize := 0
+	totalSize := 0
+	for _, c := range collections {
+		size := len(c)
+		totalSize += size
+		if size > maxSize {
+			maxSize = size
+		}
+	}
+
+	if maxSize == 0 {
+		return []T{}
+	}
+
+	result := make([]T, totalSize)
+
+	resultIdx := 0
+	for i := 0; i < maxSize; i++ {
+		for j := range collections {
+			if len(collections[j])-1 < i {
+				continue
+			}
+
+			result[resultIdx] = collections[j][i]
+			resultIdx++
+		}
+	}
+
+	return result
+}
diff --git a/slice_test.go b/slice_test.go
index 9174b0ed..5f7d872d 100644
--- a/slice_test.go
+++ b/slice_test.go
@@ -2,6 +2,7 @@ package lo
 
 import (
 	"math"
+	"reflect"
 	"strconv"
 	"strings"
 	"testing"
@@ -455,3 +456,44 @@ func TestReplaceAll(t *testing.T) {
 	is.Equal([]int{42, 1, 42, 1, 2, 3, 42}, out1)
 	is.Equal([]int{0, 1, 0, 1, 2, 3, 0}, out2)
 }
+
+func TestInterleave(t *testing.T) {
+	tests := []struct {
+		name        string
+		collections [][]int
+		want        []int
+	}{
+		{
+			"empty",
+			[][]int{},
+			[]int{},
+		},
+		{
+			"empties",
+			[][]int{{}, {}},
+			[]int{},
+		},
+		{
+			"same length",
+			[][]int{{1, 3, 5}, {2, 4, 6}},
+			[]int{1, 2, 3, 4, 5, 6},
+		},
+		{
+			"different length",
+			[][]int{{1, 3, 5, 6}, {2, 4}},
+			[]int{1, 2, 3, 4, 5, 6},
+		},
+		{
+			"many slices",
+			[][]int{{1}, {2, 5, 8}, {3, 6}, {4, 7, 9, 10}},
+			[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := Interleave(tt.collections...); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Interleave() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

From 307f0eb164cc879b193c15cfb5aea2c27fb6b3e4 Mon Sep 17 00:00:00 2001
From: dillon <dillonstreator@gmail.com>
Date: Sun, 5 Jun 2022 22:35:24 -0500
Subject: [PATCH 2/3] add nil case

---
 slice.go      | 4 ----
 slice_test.go | 5 +++++
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/slice.go b/slice.go
index 51c8337c..452765b5 100644
--- a/slice.go
+++ b/slice.go
@@ -413,10 +413,6 @@ func Interleave[T any](collections ...[]T) []T {
 		return []T{}
 	}
 
-	if len(collections) == 1 {
-		return collections[0]
-	}
-
 	maxSize := 0
 	totalSize := 0
 	for _, c := range collections {
diff --git a/slice_test.go b/slice_test.go
index 5f7d872d..df20d375 100644
--- a/slice_test.go
+++ b/slice_test.go
@@ -463,6 +463,11 @@ func TestInterleave(t *testing.T) {
 		collections [][]int
 		want        []int
 	}{
+		{
+			"nil",
+			[][]int{nil},
+			[]int{},
+		},
 		{
 			"empty",
 			[][]int{},

From 30b3e96bcb0c99a748b6ca8db518eb8f2e937233 Mon Sep 17 00:00:00 2001
From: dillonstreator <dillonstreator@gmail.com>
Date: Tue, 27 Sep 2022 19:05:54 -0500
Subject: [PATCH 3/3] Update README.md

---
 README.md | 1 -
 1 file changed, 1 deletion(-)

diff --git a/README.md b/README.md
index 4e40cab7..d068e727 100644
--- a/README.md
+++ b/README.md
@@ -59,7 +59,6 @@ GoDoc: [https://godoc.org/github.com/samber/lo](https://godoc.org/github.com/sam
 
 Supported helpers for slices:
 
-
 - [Filter](#filter)
 - [Map](#map)
 - [FilterMap](#filtermap)