349. Intersection of Two Arrays

• Difficulty: Easy

• Topics: Hash Table, Two Pointers, Binary Search, Sort

• Similar Questions:

  • Intersection of Two Arrays II

Problem:

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

Example 1:

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

Solutions:

class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        unordered_set<int> nums (nums1.begin(), nums1.end());
        unordered_set<int> ret;
        for (auto num : nums2) {
            if (nums.count(num) > 0) {
                ret.insert(num);
            }
        }

        return vector<int>(ret.begin(), ret.end());
    }
};