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my_search.py

@@ -6,4 +6,23 @@ for i in range(1, 101):
 num = random.choice(alist)
 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
 # 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):
+def binary_search(alist,num):
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+    low = 0
+    high = len(alist) - 1
+
+    while high>=low:
+        mid = (low + high) //2
+        cai = alist[mid]
+        if cai == num:
+            return mid   #返回下标位置
+        elif cai < num:
+            low = mid + 1
+        else:
+            high = mid - 1
+    return -1  #表示没找到
+
+result = binary_search(alist, num)
+if result < 0:
+    print(str(num)+"没找到")
+else:
+    print(str(num)+"找到了，下标为"+str(result))
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