save project

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=20
-low=0
-high=len(num_list)-1
-while low<=high:
-    mid=(low+high)//2
-    guess_num=num_list[mid]
-    if guess_num==num:
-        print("找到了,他在列表里的索引",mid)
-        break
-    elif guess_num<num:
-        low=mid+1
-    else:
-        high=mid-1
-        num=20
+import random
+alist=[]
+for i in range(1,101):
+    alist.append(i)
+num=random.choice(alist)
+def binary_search(alist,num):
+    low=0
+    high=len(alist)-1
+    while low<high:
+        mid=(low+high)//2
+        guess_num=alist[mid]
+        if guess_num==num:
+            return mid
+        elif guess_num<num:
+            low=mid+1
+        else:
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+            high=mid-1
+    return None
+result=binary_search(alist,num)
+print("老师给的数是",num)
+print("在列表里面的索引为",result)
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