public static void main(String[] args) {

ArrayList<Character> test = new ArrayList<Character>();

test.add('c');

test.add('b');

System.out.printf("Result: %s", test.toString());

Combination2 cb = new Combination2();

int[] num = {2,2,2};

cb.combinationSum2(num, 4);

}

public ArrayList<ArrayList<Integer>> combinationSum2(int[] num, int target) {

// first we should sort the array.

Arrays.sort(num);

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

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

cmbHelp(num, 0, path, rst, target);

return rst;

}

public void cmbHelp(int[] num, int index, ArrayList<Integer> path, ArrayList<ArrayList<Integer>> rst, int target) {

if (target == 0) {

// add the current set into the result.

rst.add(new ArrayList<Integer>(path));

}

for (int i = index; i < num.length; i++) {

if (num[i] > target) {

// don't need to add new element;

return;

}

if (i >= 1 &&

num[i] == num[i - 1] &&

(path.size() == 0 || path.get(path.size() - 1) != num[i])) {

continue;

}

path.add(num[i]);

cmbHelp(num, i + 1, path, rst, target - num[i]);

path.remove(path.size() - 1);

}

return;

}