diff --git a/_03.串/_a.串.c b/_03.串/_a.串.c
index 80432d1..922a2a7 100644
--- a/_03.串/_a.串.c
+++ b/_03.串/_a.串.c
@@ -2,7 +2,7 @@
  * @Author: Xu Bai
  * @Date: 2019-07-06 22:20:08
  * @LastEditors: Xu Bai
- * @LastEditTime: 2019-07-06 23:50:11
+ * @LastEditTime: 2019-07-07 23:05:20
  */
 
 #include "string.h"
@@ -148,6 +148,50 @@ Status SubString(String Sub, String S, int pos, int len)
     return OK;
 }
 
+int Index(String S, String T, int pos)
+{
+    // ·µ»Ø×Ó´®TÔÚÖ÷´®SÖеÚpos¸ö×Ö·ûÖ®ºóµÄλÖá£Èô²»´æÔÚ£¬Ôò·µ»Ø0
+    //ÆäÖУ¬T·Ç¿Õ£¬1¡Üpos¡ÜStrLength(S)
+    int i = pos;
+    // iÓÃÀ´Ö÷´®SÖе±Ç°Î»ÖõÄϱêÖµ£¬Èôpos²»Îª1Ôò´ÓposλÖÿªÊ¼Æ¥Åä
+    int j = 1;
+    // jÓÃÀ´×Ó´®TÖе±Ç°Î»ÖÃϱêÖµ
+    while (i <= S[0] && j <= T[0])
+    {
+        if (S[i] == T[j])
+        {
+            ++i;
+            ++j;
+        }
+        else
+        {
+            //Ö¸ÕëºóÍËÖØпªÊ¼Æ¥Åä
+            i = i - j + 2; // iÍË»ØÉÏ´ÎÆ¥ÅäÊ×λÏÂһλ
+            j = 1;         //jÍË»Ø×Ó´®TµÄÊ×λ
+        }
+    }
+    if (j > T[0])
+    {
+        return i - T[0];
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+// Status Replace(String S,String T, String V){
+//     // ÓÃVÌæ»»Ö÷´®SÖгöÏÖµÄËùÓÐÓëTÏàµÈµÄ²»ÖصþµÄ×Ó´®
+//     int i =1;
+//     if(StrEmpty(T)){
+//         return ERROR;
+//     }
+
+//     do{
+//         i=
+//     }
+// }
+
 int main()
 {
     char chars[] = "ABCD";