Submission #678557

#	Time	Username	Problem	Language	Result	Execution time	Memory
678557		tranxuanbach	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	325 ms	15520 KiB

commuter_pass

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

#define endl '\n'
#define fi first
#define se second
#define For(i, l, r) for (int i = l; i < r; i++)
#define ForE(i, l, r) for (int i = l; i <= r; i++)
#define FordE(i, l, r) for (int i = l; i >= r; i--)
#define Fora(v, a) for (auto v: a)
#define bend(a) a.begin(), a.end()
#define isz(a) ((signed)a.size())

typedef long long ll;
typedef long double ld;
typedef pair <int, int> pii;
typedef vector <int> vi;
typedef vector <pii> vpii;
typedef vector <vi> vvi;

template <class T>
using min_heap = priority_queue <T, vector <T>, greater <T>>;

const int N = 1e5 + 5;
const ll infll = (ll)1e18 + 7;

int n, m;
int s1, t1, s2, t2;
vpii adj[N];

ll dist[4][N];
ll D;

void bfs(int s, ll* dist){
    fill(dist + 1, dist + n + 1, infll);
    min_heap <pair <ll, int>> pq;
    dist[s] = 0; pq.emplace(0, s);
    while (!pq.empty()){
        ll d; int u; tie(d, u) = pq.top(); pq.pop();
        if (d != dist[u]){
            continue;
        }
        Fora(&edge, adj[u]){
            int v, w; tie(v, w) = edge;
            if (dist[v] > d + w){
                dist[v] = d + w;
                pq.emplace(dist[v], v);
            }
        }
    }
}

bool check_edge(int u, int v, int w){
    return dist[0][u] + w + dist[1][v] == D or dist[0][v] + w + dist[1][u] == D;
}

int a[N];

ll ans = infll;
ll dp[N];

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    // freopen("KEK.inp", "r", stdin);
    // freopen("KEK.out", "w", stdout);
    cin >> n >> m;
    cin >> s1 >> t1 >> s2 >> t2;
    ForE(i, 1, m){
        int u, v, w; cin >> u >> v >> w;
        adj[u].emplace_back(v, w);
        adj[v].emplace_back(u, w);
    }

    bfs(s1, dist[0]);
    bfs(t1, dist[1]);
    bfs(s2, dist[2]);
    bfs(t2, dist[3]);
    D = dist[0][t1];

    iota(a + 1, a + n + 1, 1);
    sort(a + 1, a + n + 1, [&](int u, int v){
        return dist[0][u] < dist[0][v];
    });

    fill(dp + 1, dp + n + 1, infll);
    ForE(i, 1, n){
        int u = a[i];

        Fora(&edge, adj[u]){
            int v, w; tie(v, w) = edge;
            if (check_edge(u, v, w)){
                dp[u] = min(dp[u], dp[v]);
            }
        }
        dp[u] = min(dp[u], dist[2][u]);
        ans = min(ans, dp[u] + dist[3][u]);
    }

    fill(dp + 1, dp + n + 1, infll);
    ForE(i, 1, n){
        int u = a[i];

        Fora(&edge, adj[u]){
            int v, w; tie(v, w) = edge;
            if (check_edge(u, v, w)){
                dp[u] = min(dp[u], dp[v]);
            }
        }
        dp[u] = min(dp[u], dist[3][u]);
        ans = min(ans, dp[u] + dist[2][u]);
    }

    cout << ans << endl;
}

/*
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INPUT:                                            |
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OUTPUT:                                           |
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*/

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