和为S的连续正数序列

import java.util.ArrayList;
public class Solution {
    public ArrayList<ArrayList<Integer> > FindContinuousSequence(int sum) {
       ArrayList<ArrayList<Integer>> slist=new ArrayList<>();
       ArrayList<Integer> list=new ArrayList<>(); 
        if(sum<3){//不满足至少两个连续正数合为sum
            return slist;
        }
       int small=1,big=2;//初始化双指针
       int mid=(1+sum)/2;
       int cursum=small+big;
       while(small<mid){
           if(cursum==sum){
              list=res(small,big); 
              slist.add(list);
           }
           while(cursum>sum&&small<mid){
              cursum=cursum-small; 
              small++;
                if(cursum==sum){
                list=res(small,big); 
                slist.add(list);
              }
           }
               big++;
               cursum=cursum+big;
       }
       return slist;
    }

    //添加连续正数序列中的元素
    public ArrayList<Integer> res(int small,int big){
        ArrayList<Integer> list=new ArrayList<>();
        for(int i=small;i<=big;i++){
            list.add(i);
        }
        return list;
    }

}