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.

• 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?

```public class Solution {
public int[] intersect(int[] nums1, int[] nums2) {
HashMap<Integer,Integer> map = new HashMap();
ArrayList list = new ArrayList();
for(int i=0;i<nums1.length;i++){
if(map.containsKey(nums1[i])){
map.put(nums1[i],map.get(nums1[i])+1);
}
else{
map.put(nums1[i],1);
}
}
for(int i=0;i<nums2.length;i++){
if(map.containsKey(nums2[i])){
map.put(nums2[i],map.get(nums2[i])-1);
if(map.get(nums2[i]) == 0){
map.remove(nums2[i]);
}
}
}
int[] arr = convertIntegers(list);
return arr;
}
public int[] convertIntegers(List<Integer> integers){
int[] ret = new int[integers.size()];
for (int i=0; i < ret.length; i++)
{
ret[i] = integers.get(i).intValue();
}
return ret;
}
}```

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