Count Common Words With One Occurrence

<-E 2085> Count Common Words With One Occurrence

class Solution {
public:
    int countWords(vector<string>& words1, vector<string>& words2) {
        unordered_map<string, int> mp1;
        unordered_map<string, int> mp2;
        for (auto x : words1)
            mp1[x]++;

        for (auto x : words2)
            mp2[x]++;

        int k = 0;
        for (auto x : mp1) {
            string s = x.first;
            if (mp2.find(s) != mp2.end() && mp1[s] == 1 && mp2[s] == 1)
                k++;
        }
        return k;
    }
};