不是官方题解的题解

依旧使用vector（维克托）
维克托冲锋枪

解：

#include <iostream>
#include <vector>
#include <algorithm>
#include <unordered_set>
using namespace std;
int main() {
    long long a, b, c, d;
    cin >> a >> b >> c >> d;
    long long n, m;
    cin >> n >> m;
    vector<long long> p(m);
    for (int i = 0; i < m; ++i) {
        cin >> p[i];
    }
    long long single_cost = m * a + (n - m) * c;
    unordered_set<long long> sheets;
    for (long long page : p) {
        long long sheet = (page + 1) / 2;
        sheets.insert(sheet);
    }
    long long color_sheets = sheets.size();
    long long total_sheets = (n + 1) / 2;
    long long black_sheets = total_sheets - color_sheets;
    long long double_cost = color_sheets * b + black_sheets * d;
    cout << min(single_cost, double_cost) << endl;
    return 0;
}

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