noodling on The Practice Of Programming, Chapter 2

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
+}

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()
+	}
+}

go.mod

@@ -0,0 +1,3 @@
+module tpop
+
+go 1.16