Submission #869674

#	Time	Username	Problem	Language	Result	Execution time	Memory
869674		sleepntsheep	Commuter Pass (JOI18_commuter_pass)	C++17	15 / 100	346 ms	29780 KiB

commuter_pass

#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>
#include <deque>
#include <set>
#include <utility>
#include <array>

#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx2,tune=native")



using namespace std;
#define ALL(x) x.begin(), x.end()
#define ShinLena cin.tie(nullptr)->sync_with_stdio(false);
using ll = long long;
#define N 200005

int n, m, s, t, cs, ct, head[N], e, se, shead[N];
struct edge
{
    int w, v, next;
} g[N<<1], sg[N<<1];

ll dp_s[N], dp_t[N], dp_cs[N], dp_ct[N], ans = 1e18;

void add_edge(int u, int v, int w, struct edge *g, int *e, int *h)
{
    int p = (*e)++;
    g[p] = {w, v, h[u]}; h[u] = p;
}

void add_biedge(int u, int v, int w, struct edge *g, int *e, int *h)
{
    add_edge(u, v, w, g, e, h), add_edge(v, u, w, g, e, h);
}

void dijkstra(ll *d, int s)
{
    set<pair<ll, int>> h;
    for (h.emplace(d[s] = 0, s); h.size(); )
    {
        auto [c, u] = *h.begin(); h.erase(h.begin());
        for (auto i = head[u]; i != -1; i = g[i].next)
        {
            auto [w, v, _] = g[i];
            if (c + w < d[v]) h.erase({d[v], v}), h.emplace(d[v] = c + w, v);
        }
    }
}

void init()
{
    memset(dp_s, 63, sizeof dp_s);
    memset(dp_t, 63, sizeof dp_t);
    memset(dp_cs, 63, sizeof dp_cs);
    memset(dp_ct, 63, sizeof dp_ct);
    memset(head, -1, sizeof head);
    memset(shead, -1, sizeof shead);
    ShinLena;
    cin >> n >> m >> s >> t >> cs >> ct;
    for (int u, v, w, i = 0; i < m; ++i) cin >> u >> v >> w, add_biedge(u, v, w, g, &e, head);
}

void build_shortest_path_graph()
{
    dijkstra(dp_s, s);
    dijkstra(dp_t, t);
    for (int u = 1; u <= n; ++u)
    {
        for (int j = head[u]; j != -1; j = g[j].next)
        {
            auto [w, v, _] = g[j];
            if (dp_s[u] + dp_t[v] + w == dp_s[t] || w + dp_s[v] + dp_t[u] == dp_s[t])
                add_biedge(u, v, w, sg, &se, shead);
        }
    }
}

int low[N], tin[N], timer = 1, bridge[N<<1][2], bs;

void dfs(int u, int p)
{
    low[u] = tin[u] = timer++;
    for (auto j = shead[u]; j != -1; j = sg[j].next)
    {
        auto [w, v, _] = sg[j];
        if (v == p) continue;
        if (tin[v])
        {
            low[u] = min(low[u], tin[v]);
        }
        else
        {
            dfs(v, u);
            low[u] = min(low[u], low[v]);
            if (low[v] > tin[u])
                bridge[bs][0] = u, bridge[bs][1] = v, ++bs;
        }
    }
}

void find_path()
{
    dijkstra(dp_cs, cs);
    dijkstra(dp_ct, ct);
    ll d1 = 1e18, d2 = 1e18;
    for (int i = 0; i < bs; ++i)
    {
        auto u = bridge[i][0], v = bridge[i][1];
        d1 = min({d1, dp_cs[u], dp_cs[v]});
        d2 = min({d2, dp_ct[u], dp_ct[v]});
    }
    ans = min(dp_cs[ct], d1 + d2);
}

int main()
{
    init();
    build_shortest_path_graph();
    dfs(s, s);
    find_path();
    cout << ans;

    return 0;
}

• Subtask 1: 0 / 16
• Subtask 2: 15 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45