From 137dabe066cae885427555b5a87cda7f69eb75fa Mon Sep 17 00:00:00 2001
From: huangsimin <huangsimin@youmi.net>
Date: Wed, 13 Mar 2019 14:34:20 +0800
Subject: [PATCH] =?UTF-8?q?TODO:=20=E4=BF=AE=E6=94=B9=E5=90=8E=E6=B5=8B?=
 =?UTF-8?q?=E8=AF=95=E4=B8=8D=E6=AD=A3=E7=A1=AE?=
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Content-Transfer-Encoding: 8bit

---
 avl/iterator.go | 61 +++++++++++++++++++------------------------------
 1 file changed, 24 insertions(+), 37 deletions(-)

diff --git a/avl/iterator.go b/avl/iterator.go
index 1ca8d57..a14347c 100644
--- a/avl/iterator.go
+++ b/avl/iterator.go
@@ -31,17 +31,7 @@ func (iter *Iterator) Next() (result bool) {
 			if iter.cur != nil {
 				iter.tstack.Clear()
 				iter.curPushNextStack(iter.cur)
-
-				iter.up = iter.cur
-				for iter.up != nil {
-					if iter.up.child == 1 {
-						iter.up = iter.up.parent
-						break
-					} else {
-						iter.up = iter.up.parent
-					}
-				}
-
+				iter.up = iter.getNextUp(iter.cur)
 			}
 		}
 		iter.dir = 1
@@ -50,14 +40,7 @@ func (iter *Iterator) Next() (result bool) {
 	if iter.tstack.Size() == 0 {
 		if iter.up != nil {
 			iter.tstack.Push(iter.up)
-			for iter.up != nil {
-				if iter.up.child == 1 {
-					iter.up = iter.up.parent
-					break
-				} else {
-					iter.up = iter.up.parent
-				}
-			}
+			iter.up = iter.getNextUp(iter.cur)
 		} else {
 			return false
 		}
@@ -72,6 +55,16 @@ func (iter *Iterator) Next() (result bool) {
 	return false
 }
 
+func (iter *Iterator) getNextUp(cur *Node) *Node {
+	for cur != nil {
+		if cur.child == 1 { // next 在 降序 小值. 如果child在右边, parent 比 child 小, parent才有效, 符合降序
+			return cur.parent
+		}
+		cur = cur.parent
+	}
+	return cur
+}
+
 func (iter *Iterator) curPushNextStack(cur *Node) {
 	next := cur.children[0]
 
@@ -84,6 +77,16 @@ func (iter *Iterator) curPushNextStack(cur *Node) {
 	}
 }
 
+func (iter *Iterator) getPrevUp(cur *Node) *Node {
+	for cur != nil {
+		if cur.child == 0 { // Prev 在 降序 大值. 如果child在左边, parent 比 child 大, parent才有效 , 符合降序
+			return cur.parent
+		}
+		cur = cur.parent
+	}
+	return cur
+}
+
 func (iter *Iterator) curPushPrevStack(cur *Node) {
 	prev := cur.children[1]
 
@@ -104,16 +107,7 @@ func (iter *Iterator) Prev() (result bool) {
 			if iter.cur != nil {
 				iter.tstack.Clear()
 				iter.curPushPrevStack(iter.cur)
-
-				iter.up = iter.cur
-				for iter.up != nil {
-					if iter.up.child == 0 {
-						iter.up = iter.up.parent
-						break
-					} else {
-						iter.up = iter.up.parent
-					}
-				}
+				iter.up = iter.getPrevUp(iter.cur)
 			}
 		}
 		iter.dir = -1
@@ -122,14 +116,7 @@ func (iter *Iterator) Prev() (result bool) {
 	if iter.tstack.Size() == 0 {
 		if iter.up != nil {
 			iter.tstack.Push(iter.up)
-			for iter.up != nil {
-				if iter.up.child == 0 {
-					iter.up = iter.up.parent
-					break
-				} else {
-					iter.up = iter.up.parent
-				}
-			}
+			iter.up = iter.getPrevUp(iter.cur)
 		} else {
 			return false
 		}