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binary_search.py

 # 使用二分查找法，找出9和20在列表里面的索引
 num_list = [1, 3, 5, 8, 11, 15, 17, 18, 20, 21]
-low = 0
-high = 9
-while True:
-    num = 9
+def a(num,num_list):
+    low = 0
+    high = len(num_list)-1
+    while low>=high:
         mid = (low+high)//2
         guess = num_list[mid]
         if guess == num:
-        print('找到9了：'+str(mid))
-        break
+            return mid
         elif guess > num:
             high = mid-1
         else:
             low = mid+1
-    if low>high:
-        print('找不到9')
-        break
-low = 0
-high = 9
-while True:
-    num = 20
-    mid = (low+high)//2
-    guess = num_list[mid]
-    if guess == num:
-        print('找到20了：'+str(mid))
-        break
-    elif guess > num:
-        high = mid-1
-    else:
-        low = mid+1
-    if low>high:
-        print('找不到20')
-        break
-
+x = a(18,num_list)
+print(x)
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