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my_search.py

@@ -7,3 +7,18 @@ 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):
+    low = 0  #初始最低索引值
+    high = len(alist)-1  #最高索引值
+    while low <= high:
+        mid = (low+high) // 2
+        guess = alist[mid]
+        if guess == num:   #中间值等于查找对象，返回索引
+            return mid
+        elif guess < num:
+            low = mid + 1
+        else:
+            high = mid - 1
+    return None
+result = binary_search(alist,num)
+print("老师给的数是：",num)
+print("它在列表中的索引值是：",result)
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