349. Intersection of Two Arrays

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

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

Note:

• Each element in the result must be unique.
• The result can be in any order.

解法1：

public int[] Intersection(int[] nums1, int[] nums2) {
        var hashtable = new HashSet<int>();
        foreach(var n in nums1)
        {
            hashtable.Add(n);
        }
        var res = new List<int>();
        foreach(var n in nums2 )
        {
            if(hashtable.Contains(n) && !res.Contains(n))
            {
                res.Add(n);
            }
        }
        return res.ToArray();
    }

解法2：

public int[] Intersection(int[] nums1, int[] nums2) {
        var res = new List<int>();
        Array.Sort(nums1);
        Array.Sort(nums2);
        int size1 = nums1.Count();
        int size2 = nums2.Count();
        int i = 0;
        int j = 0;
        int lastNumber =0;
        while(i<size1 && j<size2)
        {
            if(nums1[i] == nums2[j])
            {
                if(res.Count()==0 || nums1[i] != res[res.Count()-1])
                res.Add(nums1[i]);
                i++;
                j++;
            }
            else if(nums1[i] < nums2[j])
            {
                i++;
            }
            else
            {
                j++;
            }
        }
        return res.ToArray();
    }