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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
 # 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_list = [1, 3, 5, 8, 11, 15, 17, 18, 20, 21]
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+def check(n):
+    left = 0
+    right = len(num_list)-1
+    mid = 0
+    while True:
+        if right < left:
+            return "没有"
+        mid = (left+right)//2
+        num = num_list[mid]
+        if num == n:
+            return left
+        elif num < n:
+            left = mid+1
+        else:
+            right = mid-1
+print(check(20))
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