LeetCode-350. Intersection of Two Arrays II

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

Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]

Example 2:

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]

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?

题解：

go：

func intersect(nums1 []int, nums2 []int) []int {
    l1, l2 := len(nums1), len(nums2)
    m1 := make(map[int]int)
    m2 := make(map[int]int)
    res := make([]int, 0)
    for i := 0; i < l1; i++ {
        m1[nums1[i]]++
    }
    for i := 0; i < l2; i++ {
        m2[nums2[i]]++
    }
    for k, v := range m1 {
        if m2[k] > 0 {
            t := int(math.Min(float64(v), float64(m2[k])))
            for i := 0; i < t; i++ {
                res = append(res, k)
            }
        }
    }
    return res
}