Submission #649765

#	Time	Username	Problem	Language	Result	Execution time	Memory
649765		RealSnake	Commuter Pass (JOI18_commuter_pass)	C++17	55 / 100	322 ms	23676 KiB

commuter_pass

#include "bits/stdc++.h"
#define ll long long

using namespace std;

int n, m, s, t, u, v;
int a[100005];
ll dist[305][305];
vector<pair<int, ll>> node[100005];
ll ans;
int par[100005];
ll dist2[100005];

void s1() {
    for(int k = 1; k <= n; k++) {
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++) {
                if(dist[i][k] + dist[k][j] < dist[i][j])
                    dist[i][j] = dist[i][k] + dist[k][j];
            }
        }
    }
    ans = dist[u][v];
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= n; j++) {
            if(dist[s][i] + dist[i][j] + dist[j][t] == dist[s][t] || dist[s][j] + dist[j][i] + dist[i][t] == dist[s][t])
                ans = min(ans, dist[u][i] + dist[j][v]);
        }
    }
    cout << ans;
    exit(0);
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n >> m >> s >> t >> u >> v;
    if(n <= 300) {
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++)
                dist[i][j] = 1e18;
            dist[i][i] = 0;
        }
    }
    for(int i = 0; i < m; i++) {
        int a, b;
        ll c;
        cin >> a >> b >> c;
        node[a].push_back({b, c});
        node[b].push_back({a, c});
        if(n <= 300)
            dist[a][b] = dist[b][a] = c;
    }
    if(n <= 300)
        s1();
    set<pair<ll, int>> ss;
    ss.insert({0, t});
    // subtask 1 and 2
    bool b[n + 1] = {};
    b[v] = 1;
    for(int i = 1; i <= n; i++)
        dist2[i] = 1e18;
    dist2[t] = 0;
    while(ss.size()) {
        auto [dis, x] = *ss.begin();
        ss.erase(ss.begin());
        if(dis > dist2[x])
            continue;
        if(x == s)
            break;
        for(auto [y, d] : node[x]) {
            if(dis + d < dist2[y]) {
                if(y != v)
                    b[y] = b[x];
                par[y] = x;
                dist2[y] = dis + d;
                ss.insert({dist2[y], y});
            }
            else if(dis + d == dist2[y] && b[x]) {
                b[y] = b[x];
                par[y] = x;
            }
        }
    }
    swap(s, t);
    while(t != s) {
        int sz = node[t].size();
        for(int i = 0; i < sz; i++) {
            if(node[t][i].first == par[t]) {
                node[t][i].second = 0;
                break;
            }
        }
        sz = node[par[t]].size();
        for(int i = 0; i < sz; i++) {
            if(node[par[t]][i].first == t) {
                node[par[t]][i].second = 0;
                break;
            }
        }
        t = par[t];
    }
    ss.clear();
    ss.insert({0, u});
    for(int i = 1; i <= n; i++)
        dist2[i] = 1e18;
    dist2[u] = 0;
    while(ss.size()) {
        auto [dis, x] = *ss.begin();
        ss.erase(ss.begin());
        if(dis > dist2[x])
            continue;
        if(x == v) {
            cout << dis;
            return 0;
        }
        for(auto [y, d] : node[x]) {
            if(dis + d < dist2[y]) {
                dist2[y] = dis + d;
                ss.insert({dist2[y], y});
            }
        }
    }

    return 0;
}

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