feat: add BSTree which is binary search tree

datastructure/node.go

@@ -33,3 +33,15 @@ type QueueNode[T any] struct {
 func NewQueueNode[T any](value T) *QueueNode[T] {
 	return &QueueNode[T]{value, nil}
 }
+
+// TreeNode is node of tree
+type TreeNode[T any] struct {
+	Data  T
+	Left  *TreeNode[T]
+	Right *TreeNode[T]
+}
+
+// NewTreeNode return a TreeNode pointer
+func NewTreeNode[T any](data T) *TreeNode[T] {
+	return &TreeNode[T]{data, nil, nil}
+}

datastructure/tree/bstree.go

@@ -0,0 +1,51 @@
+package datastructure
+
+import (
+	"math"
+
+	"github.com/duke-git/lancet/datastructure"
+	"github.com/duke-git/lancet/lancetconstraints"
+)
+
+// BSTree is a binary search tree data structure in which each node has at most two children,
+// which are referred to as the left child and the right child.
+// In BSTree: leftNode < rootNode < rightNode
+// type T should implments Compare function of lancetconstraints.Comparator interface
+type BSTree[T any] struct {
+	root *datastructure.TreeNode[T]
+}
+
+// NewBSTree create a BSTree pointer
+func NewBSTree[T any](rootData T) *BSTree[T] {
+	root := datastructure.NewTreeNode(rootData)
+	return &BSTree[T]{root}
+}
+
+// Insert data into BSTree
+func (t *BSTree[T]) Insert(data T, comparator lancetconstraints.Comparator) {
+	root := t.root
+	newNode := datastructure.NewTreeNode(data)
+	if root == nil {
+		t.root = newNode
+	} else {
+		insertTreeNode(root, newNode, comparator)
+	}
+}
+
+// NodeLevel get node level in BSTree
+func (t *BSTree[T]) NodeLevel(node *datastructure.TreeNode[T]) int {
+	if node == nil {
+		return 0
+	}
+	left := float64(t.NodeLevel(node.Left))
+	right := float64(t.NodeLevel(node.Right))
+
+	return int(math.Max(left, right)) + 1
+}
+
+// Print the bstree structure
+func (t *BSTree[T]) Print() {
+	maxLevel := t.NodeLevel(t.root)
+	nodes := []*datastructure.TreeNode[T]{t.root}
+	printTreeNodes(nodes, 1, maxLevel)
+}

datastructure/tree/bstree_test.go

@@ -0,0 +1,29 @@
+package datastructure
+
+import "testing"
+
+type intComparator struct{}
+
+func (c *intComparator) Compare(v1, v2 any) int {
+	val1, _ := v1.(int)
+	val2, _ := v2.(int)
+
+	if val1 < val2 {
+		return -1
+	} else if val1 > val2 {
+		return 1
+	}
+	return 0
+}
+
+func TestBSTree_Insert(t *testing.T) {
+	bstree := NewBSTree(6)
+
+	comparator := &intComparator{}
+	bstree.Insert(7, comparator)
+	bstree.Insert(5, comparator)
+	bstree.Insert(2, comparator)
+	bstree.Insert(4, comparator)
+
+	bstree.Print()
+}

datastructure/tree/tree_internal.go

@@ -0,0 +1,99 @@
+package datastructure
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/duke-git/lancet/datastructure"
+	"github.com/duke-git/lancet/lancetconstraints"
+)
+
+func insertTreeNode[T any](rootNode, newNode *datastructure.TreeNode[T], comparator lancetconstraints.Comparator) {
+	if comparator.Compare(newNode.Data, rootNode.Data) == -1 {
+		if rootNode.Left == nil {
+			rootNode.Left = newNode
+		} else {
+			insertTreeNode(rootNode.Left, newNode, comparator)
+		}
+	} else {
+		if rootNode.Right == nil {
+			rootNode.Right = newNode
+		} else {
+			insertTreeNode(rootNode.Right, newNode, comparator)
+		}
+	}
+}
+
+func printTreeNodes[T any](nodes []*datastructure.TreeNode[T], level, maxLevel int) {
+	if len(nodes) == 0 || isAllNil(nodes) {
+		return
+	}
+
+	floor := maxLevel - level
+	endgeLines := int(math.Pow(float64(2), (math.Max(float64(floor)-1, 0))))
+	firstSpaces := int(math.Pow(float64(2), float64(floor))) - 1
+	betweenSpaces := int(math.Pow(float64(2), float64(floor)+1)) - 1
+
+	printSpaces(firstSpaces)
+
+	newNodes := []*datastructure.TreeNode[T]{}
+	for _, node := range nodes {
+		if node != nil {
+			fmt.Printf("%v", node.Data)
+			newNodes = append(newNodes, node.Left)
+			newNodes = append(newNodes, node.Right)
+		} else {
+			newNodes = append(newNodes, nil)
+			newNodes = append(newNodes, nil)
+			printSpaces(1)
+		}
+
+		printSpaces(betweenSpaces)
+	}
+
+	fmt.Println("")
+
+	for i := 1; i <= endgeLines; i++ {
+		for j := 0; j < len(nodes); j++ {
+			printSpaces(firstSpaces - i)
+			if nodes[j] == nil {
+				printSpaces(endgeLines + endgeLines + i + 1)
+				continue
+			}
+
+			if nodes[j].Left != nil {
+				fmt.Print("/")
+			} else {
+				printSpaces(1)
+			}
+
+			printSpaces(i + i - 1)
+
+			if nodes[j].Right != nil {
+				fmt.Print("\\")
+			} else {
+				printSpaces(1)
+			}
+			printSpaces(endgeLines + endgeLines - 1)
+		}
+		fmt.Println("")
+	}
+
+	printTreeNodes(newNodes, level+1, maxLevel)
+}
+
+// printSpaces
+func printSpaces(n int) {
+	for i := 0; i < n; i++ {
+		fmt.Print(" ")
+	}
+}
+
+func isAllNil[T any](nodes []*datastructure.TreeNode[T]) bool {
+	for _, v := range nodes {
+		if v != nil {
+			return false
+		}
+	}
+	return true
+}