save project

my_search.py

@@ -6,4 +6,19 @@ 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):
\ No newline at end of file
+def binary_search(alist,num):
+    low = 0            #最低索引
+    high = len(alist)-1#最高索引
+    while low <= high:          #当最低索引小于等于最高索引
+        mid = (low + high)//2
+        guess = alist[mid]
+        if guess == num:
+            return mid
+        elif guess < num:
+            low = mid + 1
+        else:
+            high = num - 1
+    return None
+r = binary_search(alist,num)
+print("老师给的数是：",num)
+print("在列表里的索引是：",r)