From 39b66dfd32cbb4c790cfdfa53a2d6ab9a58bbda2 Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Mon, 21 Aug 2023 15:37:05 +0800
Subject: [PATCH] code kata 230821

---
 code_kata_230821/binary_tree_test.go | 117 +++++++++++++++++++++++++++
 code_kata_230821/stack.go            |  35 ++++++++
 2 files changed, 152 insertions(+)
 create mode 100644 code_kata_230821/binary_tree_test.go
 create mode 100644 code_kata_230821/stack.go

diff --git a/code_kata_230821/binary_tree_test.go b/code_kata_230821/binary_tree_test.go
new file mode 100644
index 0000000..0b104bc
--- /dev/null
+++ b/code_kata_230821/binary_tree_test.go
@@ -0,0 +1,117 @@
+package main
+
+import "testing"
+
+func preOrder(n *node) string {
+	stack := MakeStack()
+	p := n
+	var ret string
+	for p != nil || !stack.IsEmpty() {
+		if p != nil {
+			ret += p.value
+			stack.Push(p)
+			p = p.left
+		} else {
+			p = stack.Pop().(*node)
+			p = p.right
+		}
+	}
+	return ret
+}
+
+func inOrder(n *node) string {
+	var ret string
+	stack := MakeStack()
+	p := n
+	for p != nil || !stack.IsEmpty() {
+		if p != nil {
+			stack.Push(p)
+			p = p.left
+		} else {
+			p = stack.Pop().(*node)
+			ret += p.value
+			p = p.right
+		}
+	}
+	return ret
+}
+
+func postOrder(n *node) string {
+	var ret string
+	p := n
+	stack := MakeStack()
+	var r *node
+	for p != nil || !stack.IsEmpty() {
+		if p != nil {
+			stack.Push(p)
+			p = p.left
+		} else {
+			p = stack.Top().(*node)
+			if p.right != nil && p.right != r {
+				p = p.right
+				stack.Push(p)
+				p = p.left
+			} else {
+				p = stack.Pop().(*node)
+				ret += p.value
+				r = p
+				p = nil
+			}
+		}
+	}
+	return ret
+}
+
+func TestPreOrder(t *testing.T) {
+	want := "ABDECFG"
+	got := preOrder(makeBinaryTree())
+	if got != want {
+		t.Errorf("preOrder = %s, want %s\n", got, want)
+	}
+}
+
+func TestInOrder(t *testing.T) {
+	want := "DBEAFCG"
+	got := inOrder(makeBinaryTree())
+	if got != want {
+		t.Errorf("inOrder = %s, want %s\n", got, want)
+	}
+}
+
+func TestPostOrder(t *testing.T) {
+	want := "DEBFGCA"
+	got := postOrder(makeBinaryTree())
+	if got != want {
+		t.Errorf("postOrder = %s, want %s\n", got, want)
+	}
+}
+
+func makeBinaryTree() *node {
+	return &node{
+		left: &node{
+			left: &node{
+				value: "D",
+			},
+			right: &node{
+				value: "E",
+			},
+			value: "B",
+		},
+		right: &node{
+			left: &node{
+				value: "F",
+			},
+			right: &node{
+				value: "G",
+			},
+			value: "C",
+		},
+		value: "A",
+	}
+}
+
+type node struct {
+	left  *node
+	right *node
+	value string
+}
diff --git a/code_kata_230821/stack.go b/code_kata_230821/stack.go
new file mode 100644
index 0000000..9e3414a
--- /dev/null
+++ b/code_kata_230821/stack.go
@@ -0,0 +1,35 @@
+package main
+
+type Stack []interface{}
+
+func MakeStack() *Stack {
+	return &Stack{}
+}
+
+func (s Stack) Len() int {
+	return len(s)
+}
+
+func (s Stack) IsEmpty() bool {
+	return len(s) == 0
+}
+
+func (s Stack) Top() interface{} {
+	if s.IsEmpty() {
+		return nil
+	}
+	return s[len(s)-1]
+}
+
+func (s *Stack) Push(item interface{}) {
+	*s = append(*s, item)
+}
+
+func (s *Stack) Pop() interface{} {
+	if s.IsEmpty() {
+		return nil
+	}
+	ret := (*s)[len(*s)-1]
+	*s = (*s)[:len(*s)-1]
+	return ret
+}