[Leetcode] Combination Sum III

这里只能使用1到9九个数字，并且使用的数字的个数有限制。方法类似

public class Solution {
    public void dp(List<List<Integer>> list, List<Integer> listone, int tmpsum, int start, int k, int target){
        if(tmpsum==target&&listone.size()==k){
            List<Integer> newlist = new LinkedList<Integer>();
            newlist.addAll(listone);
            list.add(newlist);
            return;
        }
        if(listone.size()==k) return;
        //listone.add(start);
        for(int s=start;s<=9;s++){
            listone.add(s);
            dp(list,listone,tmpsum+s,s+1,k,target);
            listone.remove(listone.size()-1);
        }
        //listone.remove(listone.size()-1);
        return;
    }
    public List<List<Integer>> combinationSum3(int k, int n) {
        List<List<Integer>> list = new LinkedList<List<Integer>>();
        List<Integer> listone = new LinkedList<Integer>();
        for(int i=1;i<=9;i++){
            listone.add(i);
            dp(list,listone,i,i+1,k,n);
            listone.remove(listone.size()-1);
        }
        return list;
    }
}