350. Intersection of Two Arrays II-两个数组的交集 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?

Solution in python:

class Solution:
    def intersect(self, nums1: List[int], nums2: List[int]) -> List[int]:
        adic = {}
        bdic = {}
        result = []
        for item in nums1:
            if item not in adic.keys():
                adic[item] = 1
            else:
                adic[item] += 1
        for item in nums2:
            if item not in bdic.keys():
                bdic[item] = 1
            else:
                bdic[item] += 1
        for key in bdic.keys():
            if key in adic.keys():
                count = min(adic[key], bdic[key])
                while count > 0:
                    result.append(key)
                    count -= 1
        return result