diff --git a/my_search.py b/my_search.py
index 6eaf4dc..ec5be68 100644
--- a/my_search.py
+++ b/my_search.py
@@ -6,4 +6,20 @@ for i in range(1, 101):
 num = random.choice(alist)
 # 请完善二分查找函数binary_search(),查找出num在列表alist里面的索引位置
 
-def binary_search(alist,num):
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+def binary_search(alist,num):
+    low = 0
+    high = len(alist)-1
+    while low <=high:
+        mid = (low+high) // 2
+        guess = alist[mid]
+        if guess == num:
+            return mid
+        elif guess < num:
+            low = mid + 1
+        else:
+            high = mid - 1
+    return None
+result = binary_search(alist,num)
+print("老师给的数：", num)
+print("它在列表里的索引是：", result)      
+            
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