Intersection of Two Arrays Problem & Solution

Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must be unique and you may return the result in any order.

See the intersection of two arrays problem on LeetCode.

C++ Solution

#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")

static const int _=[](){std::ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();

class Solution {
public:
  vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
    vector<bool> usage(1001, false);
    
    for (int i = 0; i < nums1.size(); ++i) {
      usage[nums1[i]] = true;
    }
    
    unordered_set<int> result;

    for (int i = 0; i < nums2.size(); ++i) {
      if (usage[nums2[i]]) {
        result.insert(nums2[i]);
      }
    }
    
    return vector<int>{result.begin(), result.end()};
  }
};

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