Submission #880832

#	Time	Username	Problem	Language	Result	Execution time	Memory
880832		vjudge1	Love Polygon (BOI18_polygon)	C++17	46 / 100	691 ms	13568 KiB

polygon

#include <bits/stdc++.h>
#define pb push_back
using namespace std;

const int N = 1e5 + 10;

int n, t, cnt, ans;
bool mark[N];
vector<int> G[N];
unordered_map<string, int> mp;

void dfs(int v) {
    mark[v] = true;
    cnt++;
    int u = G[v][0];
    while (!mark[u]) cnt++, mark[u] = true, u = G[u][0];
    return;
}

void solve() {
    bool a[21][21] = {};
    int dp[(1 << n) + 10];
    memset(dp, 63, sizeof dp);
    for (int i = 0; i < n; i++) {
        string u, v;
        cin >> u >> v;
        if (mp[u] == 0) mp[u] = ++t;
        if (mp[v] == 0) mp[v] = ++t;
        a[mp[u]][mp[v]] = true;
    }
    dp[0] = 0;
    for (int mask = 1; mask < (1 << n); mask++)
        for (int lg = 0; lg < n; lg++)
            if (mask & (1 << lg))
                for (int lg1 = 0; lg1 < n; lg1++)
                    if (mask & (1 << lg1) && lg1 ^ lg)
                        dp[mask] = min(dp[mask], dp[mask ^ (1 << lg) ^ (1 << lg1)] - a[lg + 1][lg1 + 1] - a[lg1 + 1][lg + 1] + 2);
    cout << dp[(1 << n) - 1] << '\n';
}

int main() {
    ios:: sync_with_stdio(0), cin.tie(0);
    cin >> n;
    if (n & 1) return cout << "-1\n", 0;
    if (n <= 20) {
        solve();
        return 0;
    }
    for (int i = 0; i < n; i++) {
        string u, v;
        cin >> u >> v;
        if (mp[u] == 0) mp[u] = ++t;
        if (mp[v] == 0) mp[v] = ++t;
        G[mp[u]].pb(mp[v]);
    }
    for (int i = 1; i <= n; i++)
        if (!mark[i]) {
            dfs(i);
            if (cnt ^ 2) ans += (cnt + 1) / 2;
            cnt = 0;
        }
    cout << ans << '\n';
}

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