add treesort

sorting/treesort.go

@@ -0,0 +1,63 @@
+package main
+
+import "fmt"
+
+// definition of a bst node
+type node struct {
+	val   int
+	left  *node
+	right *node
+}
+
+// definition of a node
+type btree struct {
+	root *node
+}
+
+// allocating a new node
+func newNode(val int) *node {
+	return &node{val, nil, nil}
+}
+
+// insert nodes into a binary search tree
+func insert(root *node, val int) *node {
+	if root == nil {
+		return newNode(val)
+	}
+	if val < root.val {
+		root.left = insert(root.left, val)
+	} else {
+		root.right = insert(root.right, val)
+	}
+	return root
+}
+
+// inorder traversal algorithm
+// Copies the elements of the bst to the array in sorted order
+func inorderCopy(n *node, array []int, index *int) {
+	if n != nil {
+		inorderCopy(n.left, array, index)
+		array[*index] = n.val
+		*index++
+		inorderCopy(n.right, array, index)
+	}
+}
+
+func treesort(array []int, tree *btree) {
+	// build the binary search tree
+	for _, element := range array {
+		tree.root = insert(tree.root, element)
+	}
+	index := 0
+	// perform inorder traversal to get the elements in sorted order
+	inorderCopy(tree.root, array, &index)
+}
+
+// tester
+func main() {
+	tree := &btree{nil}
+	numbers := []int{5, 4, 3, 2, 1, -1, 0}
+	fmt.Println("numbers : ", numbers)
+	treesort(numbers, tree)
+	fmt.Println("numbers : ", numbers)
+}