feat-1.0

 package xcollection
 
 import (
+	"fmt"
 	"github.com/stretchr/testify/assert"
-	"strconv"
 	"testing"
 )
 
@@ -106,21 +106,21 @@ func Test_TreeNodeByDepth(t *testing.T) {
 }
 
 type st struct {
-	Id  int
-	Pid int
+	Id  int64
+	Pid int64
 }
 
-func (t *st) PID() string {
-	return strconv.Itoa(t.Pid)
+func (t *st) PID() int64 {
+	return t.Id
 }
-func (t *st) ID() string {
-	return strconv.Itoa(t.Id)
+func (t *st) ID() int64 {
+	return t.Pid
 }
 
 func treeNodeResults(nodes []TreeNode) []string {
 	var res []string
 	for i := range nodes {
-		res = append(res, nodes[i].ID())
+		res = append(res, fmt.Sprintf("%d", nodes[i].ID()))
 	}
 	return res
 }