350. Intersection of Two Arrays II （求两个数组的交集，包含重复元素）

Given two arrays, write a function to compute their intersection.

Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2].

Note:

• Each element in the result should appear as many times as it shows in both arrays.
• The result can be in any order.

Follow up:

• What if the given array is already sorted? How would you optimize your algorithm?
• What if nums1's size is small compared to nums2's size? Which algorithm is better?

• What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?

import java.util.Hashtable;
public class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        int[] temp = new int[nums1.length];
		int index = 0;
        Map<Integer,Integer> table = new Hashtable<Integer, Integer>();
        for(int i:nums1){
        	if(table.get(i)==null)
        		table.put(i, 1);
        	else
        		table.put(i, table.get(i)+1);
        }
        for(int i:nums2){
        	if(table.get(i)!=null&&table.get(i)!=0){
        		temp[index++] = i;
        		table.put(i, table.get(i)-1);
        	}
        }
        int[] res = new int[index];
        while(index>0){
        	res[index-1] = temp[index-1];
        	index--;
        }
        return res;
    }
}