350_Intersection_of_Two_Arrays_II

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 num2’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?

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Accepted Code:

public class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        //先排序
        Arrays.sort(nums1);
        Arrays.sort(nums2);
        //确定head
        int nums1Head = 0;
        int nums2Head = 0;
        //确定输出数组
        List<Integer> resultList = new ArrayList<Integer>();
        while(nums1Head < nums1.length && nums2Head < nums2.length ){
          if(nums1[nums1Head] == nums2[nums2Head]){
            resultList.add(nums1[nums1Head]);
            nums1Head++;
            nums2Head++;
            continue;
          }else if(nums1[nums1Head] < nums2[nums2Head]){
            nums1Head++;
            continue;
          }else if(nums1[nums1Head] > nums2[nums2Head]){
            nums2Head++;
            continue;
          }
        }
        int result[] = new int[resultList.size()];
        for (int i=0; i < result.length; i++)
        {
            result[i] = resultList.get(i).intValue();
        }
        return result;
    }
}