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>> lists = new ArrayList<ArrayList<Integer>>();
        
        if (sum < 1)
            return lists;
        
        int left = 1, right = 2;
        while (left <= sum/2) {
            int cur = (left + right) * (right - left + 1) / 2;
            if (cur == sum) {
                ArrayList<Integer> list = new ArrayList<Integer>();
                for (int i=left; i<=right; i++) {
                    list.add(i);
                }
                lists.add(list);
                left ++;
            }
            else if (cur > sum) {
                left ++;
            }
            else {
                right ++;
            }
        }
       return lists;
    }
}