From 4437af52afc2289101c35027028cf5e9891df849 Mon Sep 17 00:00:00 2001
From: rihib <rihib@rihib.dev>
Date: Sun, 1 Sep 2024 18:24:31 +0900
Subject: [PATCH 1/2] pullrequests/invert_binary_tree

---
 pullrequests/invert_binary_tree/step1.go | 23 +++++++++++++++++
 pullrequests/invert_binary_tree/step2.go | 33 ++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 pullrequests/invert_binary_tree/step1.go
 create mode 100644 pullrequests/invert_binary_tree/step2.go

diff --git a/pullrequests/invert_binary_tree/step1.go b/pullrequests/invert_binary_tree/step1.go
new file mode 100644
index 0000000..baae19d
--- /dev/null
+++ b/pullrequests/invert_binary_tree/step1.go
@@ -0,0 +1,23 @@
+//lint:file-ignore U1000 Ignore all unused code
+package invertbinarytree
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+/*
+時間：3分30秒
+
+再帰的に左右のノードを入れ替えていけば良いというのにはすぐに気づき、すんなり実装することができた。
+*/
+func invertTreeStep1(root *TreeNode) *TreeNode {
+	if root == nil {
+		return nil
+	}
+	invertTreeStep1(root.Left)
+	invertTreeStep1(root.Right)
+	root.Left, root.Right = root.Right, root.Left
+	return root
+}
diff --git a/pullrequests/invert_binary_tree/step2.go b/pullrequests/invert_binary_tree/step2.go
new file mode 100644
index 0000000..8b4171c
--- /dev/null
+++ b/pullrequests/invert_binary_tree/step2.go
@@ -0,0 +1,33 @@
+//lint:file-ignore U1000 Ignore all unused code
+package invertbinarytree
+
+/*
+Step1は冗長だったのでリファクタした。
+これぐらい短いと早期リターンしなくても良いかなと思い下記のようにしました。
+またイテレーティブに解く方法も実装しました。
+*/
+func invertTreeStep2(root *TreeNode) *TreeNode {
+	if root != nil {
+		root.Left, root.Right = invertTreeStep2(root.Right), invertTreeStep2(root.Left)
+	}
+	return root
+}
+
+func invertTreeIterative(root *TreeNode) *TreeNode {
+	if root == nil {
+		return nil
+	}
+	stack := []*TreeNode{root}
+	for len(stack) > 0 {
+		node := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+		node.Left, node.Right = node.Right, node.Left
+		if node.Left != nil {
+			stack = append(stack, node.Left)
+		}
+		if node.Right != nil {
+			stack = append(stack, node.Right)
+		}
+	}
+	return root
+}

From 2ef461f9770746f0279814fe302af1fe8ef0b35a Mon Sep 17 00:00:00 2001
From: rihib <rihib@rihib.dev>
Date: Mon, 23 Sep 2024 22:45:03 +0900
Subject: [PATCH 2/2] fix pullrequests/invert_binary_tree

---
 pullrequests/invert_binary_tree/step3.go | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 pullrequests/invert_binary_tree/step3.go

diff --git a/pullrequests/invert_binary_tree/step3.go b/pullrequests/invert_binary_tree/step3.go
new file mode 100644
index 0000000..e5d894e
--- /dev/null
+++ b/pullrequests/invert_binary_tree/step3.go
@@ -0,0 +1,10 @@
+//lint:file-ignore U1000 Ignore all unused code
+package invertbinarytree
+
+func invertTreeRecursive(root *TreeNode) *TreeNode {
+	if root == nil {
+		return nil
+	}
+	root.Left, root.Right = invertTreeRecursive(root.Right), invertTreeRecursive(root.Left)
+	return root
+}