Solution.java

public class Solution {
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        Arrays.sort(candidates);
        return f(candidates,target,candidates.length-1);
    }
    public List<List<Integer>> f(int[] candidates, int target,int l) {
        List<List<Integer>> ans=new ArrayList<List<Integer>>();
        if (candidates[0]>target||target<0||l<0) {
            return ans;
        }
        for (int i =l; i >=0 ; i--) {
            int k=candidates[i];
            if (k==target) {
                List<Integer> list=new ArrayList<Integer>();
                list.add(k);
                ans.add(list);
            }else {
                List<List<Integer>> q=f(candidates,target-k,i-1);
                if (q!=null&&q.size()!=0) {
                    for (int j = 0; j < q.size(); j++) {
                        List<Integer> list=q.get(j);
                        list.add(k);
                        ans.add(list);
                    }
                }
            }
            while (i>0&&candidates[i]==candidates[i-1]) {
                i--;
            }
        }
        return ans;
    }
}