Submission #521884

#	Time	Username	Problem	Language	Result	Execution time	Memory
521884		Monarchuwu	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	378 ms	22376 KiB

commuter_pass

#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
typedef long long ll;

typedef pair<int, int> pii;
typedef pair<ll, int> pli;
#define ff first
#define ss second

const ll inf = 1e18;
const int N = 1e5 + 9;
int n, m, S, T, U, V;
vector<pii> g[N];
vector<int> G[N];

ll dist[2][N];
void dijkstra(int u, ll dist[]) {
    fill(dist + 1, dist + n + 1, inf);

    priority_queue<pli> q;
    q.emplace(dist[u] = 0, u);
    while (!q.empty()) {
        ll d = -q.top().ff; u = q.top().ss; q.pop();
        if (d != dist[u]) continue;

        for (pii v : g[u]) {
            if (dist[v.ff] > d + v.ss) {
                dist[v.ff] = d + v.ss;
                q.emplace(-dist[v.ff], v.ff);
            }
        }
    }
}

bool vis[N];
ll arr[2][N], ans(inf);
void dfs(int u) {
    vis[u] = true;
    arr[0][u] = dist[0][u]; // S->u
    arr[1][u] = dist[1][u]; // u->T

    for (int v : G[u]) {
        if (!vis[v]) dfs(v);
        arr[0][u] = min(arr[0][u], arr[0][v]);
        arr[1][u] = min(arr[1][u], arr[1][v]);
    }
    ans = min({ ans, arr[0][u] + dist[1][u], dist[0][u] + arr[1][u] });
}

int main() {
    cin.tie(NULL)->sync_with_stdio(false);
    cin >> n >> m >> S >> T >> U >> V;
    for (int i = 0, u, v, w; i < m; ++i) {
        cin >> u >> v >> w;
        g[u].emplace_back(v, w);
        g[v].emplace_back(u, w);
    }

    dijkstra(S, dist[0]);
    dijkstra(T, dist[1]);
    for (int u = 1; u <= n; ++u)
        for (pii v : g[u])
            if (dist[0][u] + v.ss + dist[1][v.ff] == dist[0][T])
                G[u].push_back(v.ff);

    dijkstra(U, dist[0]);
    dijkstra(V, dist[1]);
    for (int i = 1; i <= n; ++i)
        if (!vis[i]) dfs(i);
    cout << ans << '\n';
}
/**  /\_/\
 *  (= ._.)
 *  / >0  \>1
**/

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