350. Intersection of Two Arrays II

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

Example 1:

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

Example 2:

1 2	Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4] Output: [4,9]

Note:

1 2	Each element in the result should appear as many times as it shows in both arrays. The result can be in any order.

這題要找兩list交集，第一個想法可能會用2個for尋訪，那會得到O(nˆ2)效率不佳，而python跟javaㄧ樣有collection，其中的Counter(list)可以算list元素個數給出dict，再用&取交集，最後記得加.elements()，不然只會有單一元素。

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