diff --git a/_04.树/_c.线索二叉树.c b/_04.树/_c.线索二叉树.c
index c2431fd..8639297 100644
--- a/_04.树/_c.线索二叉树.c
+++ b/_04.树/_c.线索二叉树.c
@@ -2,7 +2,7 @@
  * @Author: Xu Bai
  * @Date: 2019-07-23 22:43:14
  * @LastEditors: Xu Bai
- * @LastEditTime: 2019-07-25 20:55:15
+ * @LastEditTime: 2019-07-26 22:36:04
  */
 #include "string.h"
 #include "stdio.h"
@@ -70,3 +70,31 @@ Status CreateBiThrTree(BiThrNode *T)
     return OK;
 }
 
+/*ȫ�ֱ�����ʼ��ָ��ոշ��ʵĽ�� */
+BiThrTree pre;
+/*���������� */
+void InThreading(BiThrTree p)
+{
+    if (p)
+    {
+        InThreading(p->lchild);
+        if (!p->lchild)
+        {
+            /*ǰ������ */
+            p->LTag = Thread;
+            /*����ָ��ָ��ǰ�� */
+            p->lchild = pre;
+        }
+        if (!pre->rchild)
+        {
+            /* ǰ��û���Һ��� */
+            /*������� */
+            pre->RTag = Thread;
+            /*ǰ���Һ���ָ���̣���ǰ���p�� */
+            pre->rchild = p;
+        }
+        /*����preָ��p��ǰ�� */
+        pre = p;
+        InThreading(p->rchild);
+    }
+}
\ No newline at end of file