save project

my_search.py

@@ -4,6 +4,17 @@ alist = []
 for i in range(1, 101):
     alist.append(i)
 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):
\ No newline at end of file
+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
+