main.cpp

/// Source : https://leetcode.com/problems/intersection-of-two-arrays-ii/description/
/// Author : liuyubobobo
/// Time   : 2017-11-14

#include <iostream>
#include <vector>
#include <unordered_map>
using namespace std;


/// Using Hash Map
/// Time Complexity: O(len(nums1) + len(nums2))
/// Space Complexity: O(len(nums1))
class Solution {
public:
    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {

        unordered_map<int, int> record;
        for(int i = 0 ; i < nums1.size() ; i ++)
            record[nums1[i]] += 1;

        vector<int> resultVector;
        for(int i = 0 ; i < nums2.size() ; i ++)
            if(record[nums2[i]] > 0){
                resultVector.push_back(nums2[i]);
                record[nums2[i]] --;
            }

        return resultVector;
    }
};


void print_vec(const vector<int>& vec){
    for(int e: vec)
        cout << e << " ";
    cout << endl;
}

int main() {

    vector<int> nums1 = {1, 2, 2, 1};
    vector<int> nums2 = {2, 2};

    print_vec(Solution().intersect(nums1, nums2));

    return 0;
}