Description

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

Example 1:

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

Solution

最简单但是
Time complexity :
O(n + m) in the average case
O(n×m) in the worst case

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

Time： O(N+M)

class Solution:
    def set_intersection(self, set1, set2):
        return [x for x in set1 if x in set2]
        
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """  
        set1 = set(nums1)
        set2 = set(nums2)
        
        if len(set1) < len(set2):
            return self.set_intersection(set1, set2)
        else:
            return self.set_intersection(set2, set1)
class Solution(object):
    def find_intersect(self,a,b):
        '''
        len a <= len b
        '''
        return [i for i in a if i in b ]
            
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        set1 = set(nums1)
        set2 = set(nums2)
        if len(set1) < len(set2):
            return self.find_intersect(set1,set2)
        else:
            return self.find_intersect(set2,set1)