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