public static void main(String[] args) {

int[] a = new int[]{2, 3, 5, 6, 7, 10};

int target = 10;

ArrayList<ArrayList<Integer>> results = new ArrayList<ArrayList<Integer>>();

ArrayList<Integer> r = new ArrayList<Integer>();

combinationSum(a, 0, target, r, results);

System.out.println(results.toString());

}

public static void combinationSum(int[] a,

int index,

int target,

ArrayList<Integer> r,

ArrayList<ArrayList<Integer>> results) {

// find it: target == 0

if (target == 0) {

results.add(new ArrayList<Integer>(r));

return;

}

if (a.length == index)

return;

combinationSum(a, index + 1, target, r, results);

int tmp = a[index];

int canUse = target / tmp;

for (int i = 1; i <= canUse; ++i) {

r.add(tmp);

combinationSum(a, index + 1, target - tmp * i, r, results);

}

for (int i = 1; i <= canUse; ++i) {

r.remove(Integer.valueOf(tmp));

}

}