一道算法面试题

import java.util.*;

public class Intersect {
    public static int[] getIntersect(int[] list1, int[] list2) {
        BitSet bs = new BitSet();
        Set<Integer> set = new HashSet<Integer>();

        for (int i = 0; i < list1.length; i++)
            bs.set(list1[i]);

        for (int i = 0; i < list2.length; i++)
            if (bs.get(list2[i]))
                set.add(list2[i]);

        int[] ret = new int[set.size()];
        int count = 0;

        for (Iterator<Integer> it = set.iterator(); it.hasNext();)
            ret[count++] = it.next();
        return ret;
    }

    public static void main(String[] args) {
        int[] list1 = { 1, 3, 5, 7, 9, 13, 18, 20, 300 };
        int[] list2 = { 2, 3, 6, 7, 10, 11, 18, 21, 3, 300 };
        int[] list3 = getIntersect(list1, list2);
        System.out.println(Arrays.toString(list3));
    }
}