LeetCode 349. Intersection of Two Arrays



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

Example 1:

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

Example 2:

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


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


Convert two lists to two sets and then find numbers which are in both sets.

Python Solution

class Solution:
    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
        results = []
        nums1 = set(nums1)
        nums2 = set(nums2)
        for num in nums2:
            if num in nums1:
        return results
  • Time Complexity: O(N).
  • Space Complexity: O(N).

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