使用等差数列的结论

import java.util.ArrayList;
import java.util.Collections;
public class Solution {
    int sum;
    public ArrayList<ArrayList<Integer> > FindContinuousSequence(int sum) {
       this.sum = sum;
        ArrayList<ArrayList<Integer>> ans = new ArrayList();
        //等差数列： N*(A中) = sum, 关键是求 (A中)，求中间那个数
        if(sum<=1) 
        {
            return ans;
        }
        for(int i=1;i<sum;++i)
        {
            int mid = sum/i;
            if((i&1)==1)
            {
               ArrayList p =  getOdd(mid,false);
               if(!p.isEmpty()) ans.add(p);
            }else{
                ArrayList p =  getOdd(mid,true);
               if(!p.isEmpty()) ans.add(p);
            }
        }
        Collections.sort(ans,(ArrayList<Integer> a,ArrayList<Integer> b)->{return a.get(0).compareTo(b.get(0));});
        return ans;

    }
    public ArrayList<Integer> getOdd(int mid,boolean even)
    {
        ArrayList<Integer> res = new ArrayList();
        if(mid==sum)
        {

            return res;
        }
        int l = mid-1,r = mid+1;
        if(even) ++l;
        int sq = l+r+mid;
        if(even) sq-=mid;
        while(sq<=sum)
        {
            if(sq==sum)
            {
                for(int i=l;i<=r&&(i>0);++i)
                {
                    if(i==0) continue;
                    res.add(i);
                }
                return res;
            }

            l--;r++;
            sq+=(l+r);


        }
        return res;



    }



}