Submission #397395

#	Time	Username	Problem	Language	Result	Execution time	Memory
397395		KoD	Love Polygon (BOI18_polygon)	C++17	25 / 100	176 ms	12308 KiB

polygon

#include <bits/stdc++.h>

template <class T>
using Vec = std::vector<T>;

int main() {
    int N;
    std::cin >> N;
    if (N % 2 == 1) {
        std::cout << -1 << '\n';
        return 0;
    }
    Vec<int> to(N);
    {
        Vec<std::string> U(N), V(N);
        for (int i = 0; i < N; ++i) {
            std::cin >> U[i] >> V[i];
        }    
        auto cmp = U;
        std::sort(cmp.begin(), cmp.end());
        for (int i = 0; i < N; ++i) {
            const auto u = std::lower_bound(cmp.cbegin(), cmp.cend(), U[i]) - cmp.cbegin();
            const auto v = std::lower_bound(cmp.cbegin(), cmp.cend(), V[i]) - cmp.cbegin();
            to[u] = v;
        }
    }
    int use = 0;
    Vec<bool> used(N);
    for (int i = 0; i < N; ++i) {
        if (!used[i]) {
            if (to[i] == i) {
                used[i] = true;
            }
            else if (to[to[i]] == i) {
                use += 1;
                used[i] = true;
            }
        }
    }
    for (int i = 0; i < N; ++i) {
        if (!used[i]) {
            int cnt = 0;
            int u = i;
            while (!used[u]) {
                cnt += 1;
                used[u] = true;
                u = to[u];
            }
            use += cnt / 2;
        }
    }
    std::cout << N - use << '\n';
    return 0;
}

• Subtask 1: 0 / 21
• Subtask 2: 25 / 25
• Subtask 3: 0 / 29
• Subtask 4: 0 / 25