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康奈尔笔记模板
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线索Cues
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笔记Notes
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Codes |
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python
1 def binary_search(list, item): 2 # low and high keep track of which part of the list you'll search in. 3 low = 0 4 high = len(list) - 1 5 6 # While you haven't narrowed it down to one element ... 7 while low <= high: 8 # ... check the middle element 9 mid = (low + high) // 2 10 我不清楚这里为什么需要两个//，正常不是一个就够了吗，然而我只用一个的时候他提醒我说索引不可以是小数 11 guess = list[mid] 12 # Found the item. 13 if guess == item: 14 return mid 15 # The guess was too high. 16 if guess > item: 17 high = mid - 1 18 # The guess was too low. 19 else: 20 low = mid + 1 21 22 # Item doesn't exist 23 return None 24 25 my_list = [1, 3, 5, 7, 9] 26 print(binary_search(my_list, 3)) # => 1 27 28 # 'None' means nil in Python. We use to indicate that the item wasn't found. 29 print(binary_search(my_list, -1)) # => None
c++
2 #include<iostream> 3 using namespace std; 4 5 int binarySearch(int data[],int length,int element) 6 { 7 //can only search an array sorted. 8 int left=0; 9 int right=length-1; 10 while(right>=left) 11 { 12 int mid=(left+right)/2; 13 int guess=data[mid]; 14 if(guess==element) 15 return mid; 16 else if(guess<element) 17 left=mid+1; 18 else 19 right=mid-1; 20 } 21 return -1; 22 } 23 24 int main() 25 { 26 int arr[]={1,2,5,9,10}; 27 int find_ele=0; 28 int length=sizeof(arr)/sizeof(int); 29 cout<<binarySearch(arr,length,find_ele)<<endl; 30 return 0; 31 }
c++（错误的办法）
2 3 int search(int arr[],int find) 4 { 5 //C++中已明确规定做为参数传递的数组名就是指针，它的大小是该类型的指针大小而非数组大小，所以不能用sizeof来求得大小 6 //解决方法：我现在还不清楚， 7 //可以进行操作，就是不可以求大小。 8 int length=sizeof(arr)/sizeof(int); 9 return binarySearch(arr,length,find); 10 } 11 12 13 int main() 14 { 15 int arr[]={1,2,5,9,10}; 16 int find_ele=2; 17 cout<<search(arr,find_ele)<<endl; 18 19 return 0; 20 }
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