Based on recursive binary search

 

description

Please write a recursive binary search algorithm to find an ordered array given an element.

Entry

A plurality of sets of data, each set of three rows of data. The first line array length n, the n second ascending behavior number, need to find third row number k. When n = 0, the input end.

Export

Each data output line, if can find a digital, output "YES", and otherwise outputs "NO".

Sample input 1

5
1 4 6 7 8
6
6
1 2 5 7 9 100
8
0

Sample output 1

YES
NO

 1 #include<iostream>
 2 using namespace std;
 3 
 4 bool binary_search(int arr[], int low, int high, int target)
 5 {
 6     if (low > high)
 7         return false;
 8     if (low <= high)
 9     {
10         int mid = (low + high) / 2;
11         if (arr[mid] == target)
12             return true;
13         else if (mid < target)
14         {
15             binary_search(arr, mid + 1, high, target);
16         }
17         else
18         {
19             binary_search(arr, low, mid - 1, target);
20         }
21     }
22 }
23 
24 int main()
25 {
26     int *arr;
27     int n, target;
28     while (cin >> n)
29     {
30         if (n == 0) break;
31         arr = new int[n + 1];
32         for (int i = 1; i <= n; i++)
33             cin >> arr[i];
34 
35         cin >> target;
36         bool flag = binary_search(arr, 1, n, target);
37         if (flag)
38             cout << "YES" << endl;
39         else
40             cout << "NO" << endl;
41         delete[]arr;
42     }
43     return 0;
44 }