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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]
 
-num = 8
+num = 18
 
 low = 0
 high = len(num_list)-1
 
 while low <= high:
     mid = (low + high) // 2
-    if mid = num:
+    guess = num_list[mid]
+    if guess == num:
         print("找到了",mid)
         break
-    elif mid < num:
+    elif guess < num:
         low = mid + 1
     else:
         high = mid -1
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