组合总和II

class Solution {
    private List<List<Integer>> res=new ArrayList<>();
    private int length;
    private int[] candidates;
    public List<List<Integer>> combinationSum2(int[] candidates,int target){
        if(candidates==null||candidates.length==0){
            return res;
        }
        Arrays.sort(candidates);
        this.length=candidates.length;
        this.candidates=candidates;
        getCombination(target,0,new Stack<>());
        return res;
    }

    public void getCombination(int residuse, int start, Stack<Integer> stack){
        if(residuse<0){
            return ;
        }
        if(residuse==0){
            List<Integer> r=new ArrayList<>(stack);
            res.add(r); 
            return;
        }
        for(int i=start;i<length&&residuse-candidates[i]>=0;i++){
            if(i>start&&candidates[i]==candidates[i-1]){
                continue;
            }
            stack.add(candidates[i]);
            getCombination(residuse-candidates[i],i+1,stack);
            stack.pop();
        }
    }
}