From 7aece75825b6ff64d06f6db41ab0889fa481db5d Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Sun, 25 Jul 2021 19:29:13 -0400
Subject: [PATCH] noodling on The Practice Of Programming, Chapter 2

---
 datastructures.go      | 72 ++++++++++++++++++++++++++++++++++++++++++
 datastructures_test.go | 25 +++++++++++++++
 go.mod                 |  3 ++
 3 files changed, 100 insertions(+)
 create mode 100644 datastructures.go
 create mode 100644 datastructures_test.go
 create mode 100644 go.mod

diff --git a/datastructures.go b/datastructures.go
new file mode 100644
index 0000000..f863519
--- /dev/null
+++ b/datastructures.go
@@ -0,0 +1,72 @@
+package main
+
+type TreeNode interface {
+	Left() TreeNode
+	Right() TreeNode
+}
+
+type BTreeNode struct {
+	left  TreeNode
+	right TreeNode
+}
+
+type StringyBTreeNode struct {
+	k string
+	v interface{}
+	BTreeNode
+}
+
+func NewStringyBTree(k string, v interface{}) *StringyBTreeNode {
+	return &StringyBTreeNode{
+		k: k,
+		v: v,
+	}
+}
+
+func (sbt *StringyBTreeNode) Left() TreeNode {
+	return sbt.left
+}
+
+func (sbt *StringyBTreeNode) Right() TreeNode {
+	return sbt.right
+}
+
+func (sbt *StringyBTreeNode) Insert(k string, v interface{}) *StringyBTreeNode {
+	if sbt.k == k {
+		sbt.v = v // set new value
+		return sbt
+	}
+	newNode := &StringyBTreeNode{k: k, v: v}
+	if sbt.k > k {
+		if sbt.left == nil {
+			sbt.left = newNode
+		} else {
+			sbt.left.(*StringyBTreeNode).Insert(k, v)
+		}
+	}
+	if sbt.k < k {
+		if sbt.right == nil {
+			sbt.right = newNode
+		} else {
+			sbt.right.(*StringyBTreeNode).Insert(k, v)
+		}
+	}
+	return sbt
+}
+
+func (sbt *StringyBTreeNode) Get(k string) interface{} {
+	if sbt.k == k {
+		return sbt.v
+	}
+	if sbt.k > k {
+		if sbt.left != nil {
+			return sbt.left.(*StringyBTreeNode).Get(k)
+		}
+	}
+	if sbt.k < k {
+		if sbt.right != nil {
+			return sbt.right.(*StringyBTreeNode).Get(k)
+		}
+	}
+	return nil // not found
+}
diff --git a/datastructures_test.go b/datastructures_test.go
new file mode 100644
index 0000000..7d25518
--- /dev/null
+++ b/datastructures_test.go
@@ -0,0 +1,25 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestBuildingTree(t *testing.T) {
+	tree := NewStringyBTree("foo", 1).Insert("bar", 2).Insert("baz", 3).Insert("quuz", 4)
+	if tree.Get("foo") != 1 {
+		t.Fail()
+	}
+	if tree.Get("bar") != 2 {
+		t.Fail()
+	}
+	if tree.Get("baz") != 3 {
+		t.Fail()
+	}
+	if tree.Get("quuz") != 4 {
+		t.Fail()
+	}
+	tree.Insert("bar", 5)
+	if tree.Get("bar") != 5 {
+		t.Fail()
+	}
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..4bd74e5
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module tpop
+
+go 1.16