Submission #160121

#	Time	Username	Problem	Language	Result	Execution time	Memory
160121		combi1k1	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	513 ms	28584 KiB

commuter_pass

#include<bits/stdc++.h>

using namespace std;

#define X   first
#define Y   second
#define ll  long long

#define FOR(i,a,b)  for(int i = a ; i < b ; ++i)

const int   N   = 1e5 + 1;
const ll    inf = 1e15;

typedef pair<ll,ll> ii;

vector<ii>  g[N];

ll  fS[N], fT[N];
ll  fU[N], fV[N];
int deg[N];

void dijkstra(int S,ll  *d) {
    FOR(i,1,N)  d[i] = inf;

    priority_queue<ii,vector<ii>,greater<ii> >  pq;

    d[S] = 0;
    pq.push(ii(0,S));

    while (pq.size())   {
        int u  = pq.top().Y;
        ll  du = pq.top().X;

        pq.pop();

        if (du != d[u])
            continue;

        for(ii  e : g[u])   {
            int v = e.X;
            int C = e.Y;
            if (d[v] > du + C)  {
                d[v] = du + C;
                pq.push({d[v],v});
            }
        }
    }
}

ll  dp1[N];
ll  dp2[N];
ll  ans = inf;

vector<int> fr[N];
vector<int> to[N];

void dfs(int u) {
    dp1[u] = fU[u];
    dp2[u] = fV[u];

    for(int v : to[u])  dp1[u] = min(dp1[u],dp1[v]);
    for(int v : to[u])  dp2[u] = min(dp2[u],dp2[v]);
    for(int v : fr[u])  {
        deg[v]--;
        if (deg[v] == 0)
            dfs(v);
    }

    ans = min(ans,dp1[u] + fV[u]);
    ans = min(ans,dp2[u] + fU[u]);
}

int main()  {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    int n, m;   cin >> n >> m;
    int S, T;   cin >> S >> T;
    int U, V;   cin >> U >> V;

    FOR(i,0,m)  {
        int x;  cin >> x;
        int y;  cin >> y;
        int c;  cin >> c;

        g[x].push_back(ii(y,c));
        g[y].push_back(ii(x,c));
    }

    dijkstra(S,fS);
    dijkstra(T,fT);
    dijkstra(U,fU);
    dijkstra(V,fV);

    FOR(i,1,n + 1)
    for(ii  e : g[i])   {
        int v = e.X;
        int C = e.Y;
        if (fS[i] + fT[v] + C == fS[T])
            fr[i].push_back(v),
            to[v].push_back(i),
            deg[v]++;
    }

    dfs(S); cout << min(ans,fU[V]) << endl;
}
/*
8 8
5 7
6 8
1 2 2
2 3 3
3 4 4
1 4 1
1 5 5
2 6 6
3 7 7
4 8 8
*/

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