修改iterator ToHead ToTail的实现, 和使用方法.

tree/avl/avl_test.go

@@ -49,11 +49,13 @@ func TestIteratorHeadTail(t *testing.T) {
 	}
 
 	iter.ToHead()
+	iter.Prev() // or iter.Next
 	if iter.Value() != 1 {
 		t.Error("iter.Value() != ", 14, " value =", iter.Value())
 	}
 
 	iter.ToTail()
+	iter.Next() // or iter.Prev()
 	if iter.Value() != 30 {
 		t.Error("iter.Value() != ", 30, " value =", iter.Value())
 	}

tree/avl/iterator.go

@@ -1,7 +1,7 @@
 package avl
 
 import (
-	"github.com/474420502/focus/stack/listarraystack"
+	lastack "github.com/474420502/focus/stack/listarraystack"
 )
 
 type Iterator struct {
@@ -31,13 +31,36 @@ func NewIteratorWithCap(n *Node, cap int) *Iterator {
 }
 
 func (iter *Iterator) ToHead() {
-	for iter.Prev() {
+	if iter.cur == nil {
+		iter.cur = iter.up
 	}
+
+	for iter.cur.parent != nil {
+		iter.cur = iter.cur.parent
+	}
+
+	for iter.cur.children[0] != nil {
+		iter.cur = iter.cur.children[0]
+	}
+	iter.SetNode(iter.cur)
+	iter.cur = nil
 }
 
 func (iter *Iterator) ToTail() {
-	for iter.Next() {
+
+	if iter.cur == nil {
+		iter.cur = iter.up
 	}
+
+	for iter.cur.parent != nil {
+		iter.cur = iter.cur.parent
+	}
+
+	for iter.cur.children[1] != nil {
+		iter.cur = iter.cur.children[1]
+	}
+	iter.SetNode(iter.cur)
+	iter.cur = nil
 }
 
 func (iter *Iterator) GetNode() *Node {