leetcode 350. Intersection of Two Arrays II ( Python )

描述

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

Example 1:

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

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.

解析

根据题意，先把两个列表排序，然后设置两个指针 i 和 j 遍历两个数组，判断是否有相同的元素，最后把结果都放入列表返回即可。时间复杂度为 O(NlogN)，空间复杂度为 O(N)。另外一种方法是用字典统计个数，然后取同在两个数组中的字符的最小出现次数，将结果放入列表总返回即可。时间复杂度为 O(N)，空间复杂度为 O(N).

解答

class Solution(object):
    def intersect(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        nums1.sort()
        nums2.sort()
        i,j=0,0
        result = []
        while i<len(nums1) and j<len(nums2):
            if nums1[i] == nums2[j]:
                result.append(nums1[i])
                i+=1
                j+=1
            elif nums1[i]>nums2[j]:
                j+=1
            elif nums1[i]<nums2[j]:
                i+=1
        return result				

运行结果

Runtime: 36 ms, faster than 69.70% of Python online submissions for Intersection of Two Arrays II.
Memory Usage: 11.9 MB, less than 31.89% of Python online submissions for Intersection of Two Arrays II.	

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