算法：搜索
描述 One day,Tom’s girlfriend give him an array A which contains N integers and asked him:Can you choose some integers from the N integers and the sum of them is equal to K.
输入There are multiple test cases.
Each test case contains three lines.The first line is an integer N(1≤N≤20),represents the array contains N integers. The second line contains N integers,the ith integer represents A[i](-10^8≤A[i]≤10^8).The third line contains an integer K(-10^8≤K≤10^8).输出If
Tom can choose some integers from the array and their them is K,printf ”Of course,I can!”; other printf ”Sorry,I can’t!”.样例输入4
1 2 4 7
13
4
1 2 4 7
15
样例输出
Of course,I can!
Sorry,I can't!
代码：
#include <iostream>
#include <string>
#include <cstring>
#include <algorithm>
#include <iomanip>
using namespace std;
int n,m,a[25],flag;
int dfs(int i,int sum)
{
if(i==n)
return sum==m;
if(dfs(i+1,sum))
return 1;
if(dfs(i+1,sum+a[i]))
return 1;
return 0; }
int main()
{
int i,j,k;
while(cin>>n)
{
for(i=0;i<n;i++)
cin>>a[i];
cin>>m;
if(dfs(0,0)) cout<<"Of course,I can!"<<endl;
else cout<<"Sorry,I can't!"<<endl;
}
return 0;
}