Submission #649688

#	Time	Username	Problem	Language	Result	Execution time	Memory
649688		RealSnake	Commuter Pass (JOI18_commuter_pass)	C++17	0 / 100	2087 ms	15312 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[100005], dist2[100005], distt[305][305];
vector<pair<int, ll>> node[100005], node2[100005];
int ind;
ll ans = 1e18;

void solve() {
    for(int i = 0; i < ind - 1; i++) {
        int b1 = a[i], b2 = a[i + 1];
        int sz = node[b1].size();
        for(int j = 0; j < sz; j++) {
            if(node2[b1][j].first == b2) {
                node2[b1][j].second = 0;
                break;
            }
        }
        sz = node[b2].size();
        for(int j = 0; j < sz; j++) {
            if(node2[b2][j].first == b1) {
                node2[b2][j].second = 0;
                break;
            }
        }
    }
    set<pair<ll, int>> ss;
    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 || dis >= ans) {
            ans = min(ans, dis);
            break;
        }
        for(auto [y, d] : node2[x]) {
            if(dis + d < dist2[y]) {
                dist2[y] = dis + d;
                ss.insert({dist2[y], y});
            }
        }
    }
    for(int i = 0; i < ind - 1; i++) {
        int b1 = a[i], b2 = a[i + 1];
        int sz = node[b1].size();
        for(int j = 0; j < sz; j++) {
            if(node2[b1][j].first == b2) {
                node2[b1][j].second = node[b1][j].second;
                break;
            }
        }
        sz = node[b2].size();
        for(int j = 0; j < sz; j++) {
            if(node2[b2][j].first == b1) {
                node2[b2][j].second = node[b2][j].second;
                break;
            }
        }
    }
}

void dfs(int x) {
    a[ind++] = x;
    if(x == t) {
        solve();
        return;
    }
    for(auto [y, d] : node[x]) {
        if(dist[x] + d <= dist[y]) {
            dist[y] = dist[x] + d;
            dfs(y);
        }
    }
    ind--;
}

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

    cin >> n >> m >> s >> t >> u >> v;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= n; j++)
            distt[i][j] = 1e18;
        distt[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});
        node2[a].push_back({b, c});
        node2[b].push_back({a, c});
        distt[a][b] = distt[b][a] = c;
    }
    for(int k = 1; k <= n; k++) {
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++) {
                if(distt[i][k] + distt[k][j] < distt[i][j])
                    distt[i][j] = distt[i][k] + distt[k][j];
            }
        }
    }
    for(int i = 1; i <= n; i++)
        dist[i] = distt[s][i];
    dfs(s);
    cout << ans;

    return 0;
}

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