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a.py

+num_list = [1, 3, 5, 8, 11, 15, 17, 18, 20, 21]
+
+
+def ercha(name_list,goal):
+    low=0
+    hight=len(name_list)-1
+    while low<=hight:
+        mid=(low+hight)//2
+        num=name_list[mid]
+        if num==goal:
+            return mid
+        elif num<goal:
+            low=mid+1
+        else:
+            high=mid-1
+    return None 
+res=ercha(num_list,20)  
+print(res) 
\ No newline at end of file

defin.py

@@ -27,7 +27,7 @@ def erfen(alist,number):
         mid = (low+high)//2
         num = alist[mid]
         if num == number:
-            print("索引:",mid)
+            #print("索引:",mid)
             return mid
             #break
         
@@ -36,5 +36,5 @@ def erfen(alist,number):
         else:
             high = mid-1   
     return None
-res = erfen(num_list,2)
-print(res)
+res = erfen(num_list,1)
+print("索引:",res)

guess_num.py

+import random
+
+alist = []
+for i in range(1, 101):
+    alist.append(i)
+num = random.choice(alist)
+# 请完善二分查找函数binary_search(),查找出num在列表alist里面的索引位置
+
+def binary_search(alist,num):
+    low = 0         # 初始最低索引
+    high = len(alist)-1          # 初始最高索引
+    while low <= high:      # 当最低索引小于等于最高索引
+        mid = (low + high) // 2
+        guess = alist[mid]
+        if guess == num:        # 中间值等于查找对象，返回索引
+            return mid
+        elif guess < num:       # 中间值小于查找对象
+            low = mid + 1
+        else:                   # 中间值大于查找对象
+            high = mid - 1
+    return None
+
+result = binary_search(alist, num)
+print("老师给的数是：", num)
+print("它在列表里的索引是：", result)       # 列表从1开始，索引从0开始，所以少1
\ No newline at end of file

t.py

@@ -11,14 +11,19 @@ else:
 
 # 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]
+
+#要查找的数
 goal = 20
 low = 0
 high = len(num_list)-1
+
 while low<=high:
+    #取中间值的索引位置
     mid = (low+high)//2
+    #取中间值
     num = num_list[mid]
     if num==goal:
-        print("索引",mid)
+        print("索引：",mid)
         break
     elif num<goal:
         low = mid+1
@@ -26,3 +31,4 @@ while low<=high:
         high = mid-1
 
 
+