Submission #482587

#	Time	Username	Problem	Language	Result	Execution time	Memory
482587		jalsol	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	253 ms	25264 KiB

commuter_pass

#ifdef LOCAL
#include "local.h"
#else
#include <bits/stdc++.h>
#define debug(...)
#define DB(...)
#endif

using namespace std;

const bool __initialization = []() {
    cin.tie(nullptr)->sync_with_stdio(false);
#define TASK "empty"
    if (fopen(TASK".inp", "r")) {
        (void)(!freopen(TASK".inp", "r", stdin));
        (void)(!freopen(TASK".out", "w", stdout)); }
    cout << setprecision(12) << fixed;
    return true;
}();

using ll = long long;
using ld = long double;

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()

#define For(i, l, r) for (int i = (l); i <= (r); ++i)
#define Ford(i, r, l) for (int i = (r); i >= (l); --i)
#define Rep(i, n) For (i, 0, (n) - 1)
#define Repd(i, n) Ford (i, (n) - 1, 0)
#define Fe(...) for (auto __VA_ARGS__)

template <class C> inline int isz(const C& c) { return static_cast<int>(c.size()); }
template <class T> inline bool chmin(T& a, const T& b) { return (a > b) ? a = b, true : false; }
template <class T> inline bool chmax(T& a, const T& b) { return (a < b) ? a = b, true : false; }

constexpr ld eps = 1e-9;
constexpr int inf = 1e9;
constexpr ll linf = 1e18;

// =============================================================================

constexpr int maxn = 1e5 + 5;

struct Link {
    int v, c;
};

struct Data {
    int u; ll du;

    bool operator<(const Data& o) const {
        return du > o.du;
    }
};

int n, ne;
int src, dest;
int U, V;
vector<Link> g[maxn];

ll ds[maxn], dU[maxn], dV[maxn];
priority_queue<Data> q;

void Dijkstra(int s, ll* d) {
    memset(d + 1, 0x3f, sizeof(ll) * n);
    d[s] = 0;
    q.push({s, d[s]});

    while (isz(q)) {
        auto [u, du] = q.top(); q.pop();
        if (du != d[u]) continue;

        Fe (&[v, c] : g[u]) {
            if (chmin(d[v], d[u] + c)) {
                q.push({v, d[v]});
            }
        }
    }
}

ll ans;
bool vis[maxn], visDest[maxn];
ll dpU[maxn], dpV[maxn];

void Dfs(int u) {
    if (vis[u]) return;
    vis[u] = true;

    dpU[u] = dpV[u] = linf;
    if (u == dest) visDest[u] = true;

    Fe (&[v, c] : g[u]) {
        if (ds[v] != ds[u] + c) continue;

        Dfs(v);
        if (visDest[v]) {
            visDest[u] = true;
            chmin(dpU[u], dpU[v]);
            chmin(dpV[u], dpV[v]);
        }
    }

    if (visDest[u]) {
        chmin(ans, dpU[u] + dV[u]);
        chmin(ans, dpV[u] + dU[u]);
        chmin(dpU[u], dU[u]);
        chmin(dpV[u], dV[u]);
    }
}

signed main() {
    cin >> n >> ne;
    cin >> src >> dest;
    cin >> U >> V;

    Rep (_, ne) {
        int u, v, c; cin >> u >> v >> c;
        g[u].push_back({v, c});
        g[v].push_back({u, c});
    }

    Dijkstra(src, ds);
    Dijkstra(U, dU);
    Dijkstra(V, dV);

    ans = dU[V];
    Dfs(src);
    cout << ans << '\n';
}

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