P30：部分和问题

 

 

 

/*
    P30页：部分和问题
    核心：用递归实现深度优先搜索是很方便的事情
    问题：n个数中选出任意个数使得和为k, 找到返回find，灭有返回not find
*/
#include <iostream>
#include <iterator>
#include <vector>
using namespace std;
const int NUM = 1010;

int n, k;
int a[NUM];
vector<int> s;
bool bfs(int i, int sum)
{
    if(i == n)
        return sum == k;
    if (bfs(i+1, sum))
        return true;
    if (bfs(i+1, sum+a[i]))
    {
        s.insert(s.end(), a[i]);
        return true;
    }

    return false;
}

int main(void)
{
    cin >> n >> k;
    for(int i = 0; i < n; i++)
        cin >> a[i];

    if (bfs(0, 0))
    {
        copy(s.begin(), s.end(), ostream_iterator<int>(cout, "+"));
        cout << "=" << k << "\n" << "find" << "\n";
    }
    else
        cout << "not find";
    return 0;
}