feat: add BSTree which is binary search tree

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
+}