중복 없는 공통 품목

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

void prepare(vector<int>& values) {
    sort(values.begin(), values.end());
    values.erase(unique(values.begin(), values.end()), values.end());
}
int solution(vector<int> first, vector<int> second) {
    prepare(first); prepare(second);
    int i = 0, j = 0, answer = 0;
    while (i < (int)first.size() && j < (int)second.size()) {
        if (/*@blank1@*/) ++i;
        else if (first[i] > second[j]) ++j;
        else {
            ++answer;
            /*@blank2@*/
        }
    }
    return answer;
}
int main() {
    int n, m; cin >> n >> m;
    vector<int> first(n), second(m);
    for (int i = 0; i < n; ++i) cin >> first[i];
    for (int i = 0; i < m; ++i) cin >> second[i];
    cout << solution(first, second) << '\n';
    return 0;
}