From 12e2ab5e0f86882e21ff39ef242d8f590bd41abc Mon Sep 17 00:00:00 2001
From: "legolas.zhan" <legolas.zhan@webeye.cn>
Date: Mon, 2 Dec 2024 17:11:37 +0800
Subject: [PATCH 1/2] 117. Populating Next Right Pointers in Each Node II

---
 leetcode/others/connect.go      | 34 ++++++++++++++
 leetcode/others/connect_test.go | 79 +++++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 leetcode/others/connect.go
 create mode 100644 leetcode/others/connect_test.go

diff --git a/leetcode/others/connect.go b/leetcode/others/connect.go
new file mode 100644
index 00000000..8d5b5eba
--- /dev/null
+++ b/leetcode/others/connect.go
@@ -0,0 +1,34 @@
+package lothers
+
+type Node struct {
+	Val   int
+	Left  *Node
+	Right *Node
+	Next  *Node
+}
+
+func connect(root *Node) *Node {
+	if root == nil {
+		return nil
+	}
+
+	queue := []*Node{root}
+	for len(queue) > 0 {
+		levelSize := len(queue)
+		for i := 0; i < levelSize; i++ {
+			node := queue[i]
+			if i < levelSize-1 {
+				node.Next = queue[i+1]
+			}
+
+			if node.Left != nil {
+				queue = append(queue, node.Left)
+			}
+			if node.Right != nil {
+				queue = append(queue, node.Right)
+			}
+		}
+		queue = queue[levelSize:]
+	}
+	return root
+}
diff --git a/leetcode/others/connect_test.go b/leetcode/others/connect_test.go
new file mode 100644
index 00000000..f69f7a39
--- /dev/null
+++ b/leetcode/others/connect_test.go
@@ -0,0 +1,79 @@
+package lothers
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConnect(t *testing.T) {
+	tests := []struct {
+		name     string
+		root     *Node
+		expected []interface{}
+	}{
+		{
+			name: "Example 1",
+			root: &Node{
+				Val: 1,
+				Left: &Node{
+					Val: 2,
+					Left: &Node{
+						Val: 4,
+					},
+					Right: &Node{
+						Val: 5,
+					},
+				},
+				Right: &Node{
+					Val: 3,
+					Right: &Node{
+						Val: 7,
+					},
+				},
+			},
+			expected: []interface{}{1, "#", 2, 3, "#", 4, 5, 7, "#"},
+		},
+		{
+			name:     "Example 2",
+			root:     nil,
+			expected: []interface{}{},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			root := connect(tt.root)
+
+			// Serialize the tree and check the result
+			result := serializeTree(root)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func serializeTree(root *Node) []interface{} {
+	if root == nil {
+		return []interface{}{}
+	}
+	queue := []*Node{root}
+	var result []interface{}
+	for len(queue) > 0 {
+		levelSize := len(queue)
+		for i := 0; i < levelSize; i++ {
+			node := queue[i]
+			result = append(result, node.Val)
+			if i == levelSize-1 {
+				result = append(result, "#")
+			}
+			if node.Left != nil {
+				queue = append(queue, node.Left)
+			}
+			if node.Right != nil {
+				queue = append(queue, node.Right)
+			}
+		}
+		queue = queue[levelSize:]
+	}
+	return result
+}

From ae26ea48fd7588c2c1632968fe76fdde19b4ffa0 Mon Sep 17 00:00:00 2001
From: "legolas.zhan" <legolas.zhan@webeye.cn>
Date: Mon, 2 Dec 2024 17:15:44 +0800
Subject: [PATCH 2/2] 117. only use constant extra space

---
 leetcode/others/connect.go | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/leetcode/others/connect.go b/leetcode/others/connect.go
index 8d5b5eba..64361dca 100644
--- a/leetcode/others/connect.go
+++ b/leetcode/others/connect.go
@@ -12,23 +12,23 @@ func connect(root *Node) *Node {
 		return nil
 	}
 
-	queue := []*Node{root}
-	for len(queue) > 0 {
-		levelSize := len(queue)
-		for i := 0; i < levelSize; i++ {
-			node := queue[i]
-			if i < levelSize-1 {
-				node.Next = queue[i+1]
-			}
+	current := root
+	for current != nil {
+		dummy := &Node{}
+		tail := dummy
 
+		for node := current; node != nil; node = node.Next {
 			if node.Left != nil {
-				queue = append(queue, node.Left)
+				tail.Next = node.Left
+				tail = tail.Next
 			}
 			if node.Right != nil {
-				queue = append(queue, node.Right)
+				tail.Next = node.Right
+				tail = tail.Next
 			}
 		}
-		queue = queue[levelSize:]
+		current = dummy.Next
 	}
+
 	return root
 }