Submission #1088315

#	Time	Username	Problem	Language	Result	Execution time	Memory
1088315		JanPham	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	212 ms	28564 KiB

commuter_pass

#include <iostream>
#include <vector>
#include <queue>

using namespace std;

#define int long long
const int N = 1e5 + 10;
#define ll long long
#define li pair <ll, int>

int n, m, a, b, c, d;
int x, y;
ll k;
vector <li> v[N];
ll disA[N], disB[N], disC[N], disD[N];

void dijkstra(int s, ll dis[]) {
    fill_n(dis, N, 4e18);
    dis[s] = 0;

    priority_queue < li, vector <li>, greater <li> > q;
    q.push(li(0, s));

    while (!q.empty()) {
        li p = q.top(); q.pop();
        int u = p.second;
        ll w = p.first;

        if (dis[u] < w) continue;

        for (li z: v[u]) {
            if (z.first + w < dis[z.second]) {
                dis[z.second] = z.first + w;
                q.push(li(dis[z.second], z.second));
            }
        }
    }
}

void pre() {
    dijkstra(a, disA);
    dijkstra(b, disB);
    dijkstra(c, disC);
    dijkstra(d, disD);
}

ll dp[2][N], best = 4e18;
bool vis[N];
void dfs(int s) {
    vis[s] = true;
    dp[0][s] = dp[1][s] = 4e18;

    for (li i: v[s]) {
        int z = i.second;
        if (disA[s] + disB[z] + i.first != disA[b]) continue;

        if (!vis[z]) {
            dfs(z);
        }
        dp[0][s] = min(dp[0][s], dp[0][z]);
        dp[1][s] = min(dp[1][s], dp[1][z]);
    }

    best = min(best, disC[s] + dp[1][s]);
    best = min(best, dp[0][s] + disD[s]);

    dp[0][s] = min(dp[0][s], disC[s]);
    dp[1][s] = min(dp[1][s], disD[s]);
}

void solve() {
    best = disC[d];
    dfs(a);
    cout << best << "\n";
}

signed main() {
    if (fopen("bus.inp", "r")) {
        freopen("bus.inp", "r", stdin);
        freopen("bus.out", "w", stdout);
    }

    cin.tie(nullptr);
    cout.tie(nullptr);
    ios_base::sync_with_stdio(false);

    cin >> n >> m >> a >> b >> c >> d;
    for (int i = 1; i <= m; ++i) {
        cin >> x >> y >> k;
        v[x].push_back(li(k, y));
        v[y].push_back(li(k, x));
    }

    pre();
    solve();

    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:80:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |         freopen("bus.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:81:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |         freopen("bus.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45