Union and Intersection of two sorted lists 并集和交集

跟面试官确认是arrayList还是singly-linked list

/*
  Union 并集：两个升序的list a, b, 返回其并集（升序排序）
*/

public class UnionTwoSortedLists {
    public  List<Integer> union(List<Integer> a, List<Integer> b) {
        List<Integer> result = new ArrayList<>();
        // Use two index variables i and j, initial values i = 0, j = 0
        int i = 0, j = 0;
        while (i < a.size() && j < b.size()) {
            // If a.get(i) < b.get(j) then add a.get(i) to result and increment i.
            if (a.get(i) < b.get(j)) {
                result.add(a.get(i));
                i++;
            }
            // If b.get(j) < a.get(i) then add b.get(j) to result and increment j.
            else if (b.get(j) < a.get(i)) {
                result.add(b.get(j));
                j++;

            }
            // If both are same then add any to result and increment both i and j.
            else {
                result.add(b.get(j));
                i++;
                j++;
            }
        }
       /* handle the case a.size()!= b.size(), add remaining elements of the larger array */
        while (i < a.size()){
            result.add(a.get(i));
            i++;
        }
        while (j  < b.size()){
            result.add(b.get(j));
            j++;
        }
        return result;
    }

    public static void main(String[] args) {
        List<Integer> l1 = new ArrayList<>();
        l1.add(1);
        l1.add(2);
        l1.add(3);
        List<Integer> l2 = new ArrayList<>();
        l2.add(2);
        l2.add(3);
        UnionTwoSortedLists test = new UnionTwoSortedLists();
        for(int n : test.union(l1,l2)){
            System.out.println(n);
        }
    }
}

/*
   Intersection 交集：两个升序的list a, b, 返回其交集（升序排序）

*/

public class IntersectionTwoSortedLists {

    public List<Integer> intersection(List<Integer> a, List<Integer> b) {
        List<Integer> result = new ArrayList<>();
        // Use two index variables i and j, initial values i = 0, j = 0
        int i = 0, j = 0;
        while (i < a.size() && j < b.size()) {
            // If a.get(i) < b.get(j) then increment i.
            if (a.get(i) < b.get(j)) {
                i++;
            }
            // If b.get(j) < a.get(i) then increment j.
            else if (b.get(j) < a.get(i)) {
                j++;

            }
            // If both are same then add any to result and increment both i and j.
            else {
                result.add(b.get(j));
                i++;
                j++;
            }
        }
        return result;
    }

    public static void main(String args[]) {
        List<Integer> l1 = new ArrayList<>();
        l1.add(1);
        l1.add(2);
        l1.add(3);
        List<Integer> l2 = new ArrayList<>();
        l2.add(2);
        l2.add(5);
        IntersectionTwoSortedLists test = new IntersectionTwoSortedLists();
        for (int n : test.intersection(l1, l2)) {
            System.out.println(n);
        }
    }
}

followup1: 上述问题是2个list,  求问n个list的union和intersection