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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]
+# goal = 20
+# low = 0
+# high = len(num_list)-1
+def check(alist,number):
+    low = 0
+    high = len(alist)-1
+    while low<=high:
+        mid = (low+high)//2
+        num = alist[mid]
+        if num == number:
+            return mid
+           # break
+        elif num<number:
+            low = mid+1
+        else:
+            high = mid-1
+    return None
+res = check(num_list,21)
+print(res)
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