数字组合

输入一个整形数组 和一个目标数字。要求打印出所有用给定数组内的数字的和等于给定目标数字的组合，给定数组内的每个数字使用次数不限。如输入数组{2, 3}，目标数字12,。则应打印出：{3, 3, 3, 3},  {3, 3, 2, 2, 2},  {2, 2, 2, 2, 2, 2}。

#include <iostream>
#include <string>
#include <map>
#include <vector>
using namespace std;

void fun(int a[], int n, int &pos, int &value, int target, vector<int> &buf, map<int,int> locs)
{
	if (value == target)
	{
		for (int i = 0; i < buf.size(); i++)
		{
			cout << buf[i] << " ";
		}
		cout << endl;
	}

    if (pos >= 0 && value < target)
	{
		buf.push_back(a[pos]);
		value += a[pos];
		fun(a, n, pos, value, target, buf, locs);
	}
	else
	{
        if (buf[0] == a[0])
		{
			return;
		}
		while (buf[buf.size()-1] == a[0])
		{
            value -= buf[buf.size()-1];
		    buf.pop_back();
		}

		pos = locs[buf[buf.size()-1]] - 1;
		value -= buf[buf.size()-1];
		buf.pop_back();

		fun(a, n, pos, value, target, buf, locs);
	}
}

int main()
{
	int a[] = {2,3};
	int value = 0;
	int target = 12;
	vector<int> buf;
	map<int,int> locs;
	int n = sizeof(a)/sizeof(a[0]);
	int pos = n-1;
	for (int i = 0; i < n; i++)
	{
		locs[a[i]] = i;
	}
	fun(a, n, pos, value, target, buf, locs);

	return 0;
}