LeetCode精选100题——第39题——组合总和_苏绛毓组合100题

class Solution {
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        ArrayList<List<Integer>> res=new ArrayList<>();
        if(candidates==null||candidates.length==0){
            return res;
        }
        helper(res,new ArrayList<Integer>(),candidates,target,0);
        return res;
    }
    private void helper(ArrayList<List<Integer>> res,ArrayList<Integer> list,int[] candidates,int target,int start){
        if(target==0){
            res.add(new ArrayList(list));
            return;
        }
        if(target<0){
            return;
        }
        for(int i=start;i<candidates.length;i++){
            list.add(candidates[i]);
            helper(res,list,candidates,target-candidates[i],i);
            list.remove(list.size()-1);
        }
    }
}
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