349.md

349. Intersection of Two Arrays

难度: Easy

刷题内容

原题连接

• https://leetcode.com/problems/intersection-of-two-arrays/

内容描述

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]
Note:

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

解题方案

思路 1 - 时间复杂度: O(m * n) - 空间复杂度: O(1)

时间就看python set intersection的时间了，平均O(min(m, n))，最坏O(m * n)

Python一句话作弊,beats 82.08%

class Solution(object):
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        return list(set(nums1).intersection(nums2))

思路 2 - 时间复杂度: O(m + n) - 空间复杂度: O(m)

Counter, beats 82.08%

class Solution:
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        import collections
        lookup = collections.Counter(nums1)
        res = set()
        for num in nums2:
            if num in lookup:
                res.add(num)
        return list(res)

或者不借用Counter

beats 99.88%

class Solution:
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        a = set(nums1)
        b = set(nums2)
        res = []
        for i in a:
            if i in b:
                res.append(i)
        return res