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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]
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+num_list = [1, 3, 5, 8, 11, 15, 17, 18, 20, 21]
+def two(alist,num):
+    low = 0
+    high = len(alist)-1  
+    while low < high:    
+        mid = (low+high)//2     
+        guess = alist[mid]    
+        if guess==num:     
+            return mid
+        if guess<num:   
+            low = mid + 1
+        else:
+            high = mid - 1
+r = two(num_list,20)
+print(r)
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