Submission #1093080

#	Time	Username	Problem	Language	Result	Execution time	Memory
1093080		ortsac	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	1 ms	348 KiB

ho_t4

#include <bits/stdc++.h>

using namespace std;

#define int long long
int INF = 0x3f3f3f3f3f3f3f3f;

struct Edge {
    int to, c, d;
    Edge(int x = 0, int y = 0, int z = 0) : to(x), c(y), d(z) {}
};

const int MAXN = 205;
int gnode[MAXN][MAXN];
int gc[MAXN][MAXN];
int comp[MAXN];
bool vis[MAXN];
int currC = 0;
vector<Edge> adj1[MAXN], adj[MAXN];
int n, m;

void dfs1(int node, int p) {
    vis[node] = 1;
    gnode[p][node] = 1;
    for (auto u : adj1[node]) {
        if (!vis[u.to]) dfs1(u.to, p);
    }
}

void calcComp(int node) {
    if (comp[node]) return;
    comp[node] = currC;
    for (int i = 1; i <= n; i++) {
        if (gnode[node][i] && gnode[i][node]) calcComp(i);
    }
}

int32_t main() {
    freopen("in", "r", stdin);
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int a, b, c, d;
        cin >> a >> b >> c >> d;
        adj1[a].push_back(Edge(b, c, d));
    }
    for (int i = 1; i <= n; i++) {
        memset(vis, 0, sizeof vis);
        dfs1(i, i);
    }
    for (int i = 1; i <= n; i++) {
        if (comp[i]) continue;
        currC++;
        calcComp(i);
    }
    if (comp[1] == comp[n]) {
        cout << "0\n";
        return 0;
    }
    if (!(gnode[1][n] || gnode[n][1])) {
        cout << "-1\n";
        return 0;
    }
    for (int i = 1; i <= n; i++) {
        for (auto u : adj1[i]) {
            adj[comp[i]].push_back(Edge(comp[u.to], u.c, u.d));
        }
    }
    int ans = INF;
    int qtd = 0, mi = INF;
    for (auto u : adj[comp[1]]) {
        if (u.to == comp[n]) {
            qtd++;
            mi = min(mi, u.d);
        }
    }
    if (qtd >= 2) ans = min(ans, mi);
    // duas saindo do N
    qtd = 0, mi = INF;
    for (auto u : adj[comp[n]]) {
        if (u.to == comp[1]) {
            qtd++;
            mi = min(mi, u.d);
        }
    }
    if (qtd >= 2) ans = min(ans, mi);
    // componente intermediaria
    for (int i = 1; i <= currC; i++) {
        for (int j = 1; j <= currC; j++) {
            gc[i][j] = INF;
        }
        for (auto u : adj[i]) {
            gc[i][u.to] = min(gc[i][u.to], u.d);
        }
    }
    int s = comp[1], t = comp[n];
    if (!gnode[1][n]) swap(s, t);
    for (int i = 1; i <= currC; i++) {
        if ((i == s) || (i == t)) continue;
        if (gc[t][i] != INF) {
                ans = min(ans, gc[s][i]);
        }
        if (gc[i][s] != INF) {
                ans = min(ans, gc[i][t]);
        }
    }
    // cout resposta
    if (ans == INF) cout << "-1\n";
    else cout << ans << "\n";
}

Compilation message (stderr)

ho_t4.cpp: In function 'int32_t main()':
ho_t4.cpp:39:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   39 |     freopen("in", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63