349. Intersection of Two Arrays*

349. Intersection of Two Arrays*

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

题目描述

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.

C++ 实现 1

class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        vector<int> res;
        unordered_set<int> set1(nums1.begin(), nums1.end()),
                        set2(nums2.begin(), nums2.end());
        for (auto &n : set1)
            if (set2.count(n)) res.push_back(n);
        return res;
    }
};

C++ 实现 2

也可以这样:

class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        unordered_set<int> r1, r2;
        for (auto &n : nums1) r1.insert(n);
        for (auto &n : nums2)
            if (r1.count(n)) r2.insert(n);
        vector<int> res(r2.begin(), r2.end());
        return res;
    }
};