Submission #927802

#	Time	Username	Problem	Language	Result	Execution time	Memory
927802		Unforgettablepl	Olympic Bus (JOI20_ho_t4)	C++17	5 / 100	56 ms	4188 KiB

ho_t4

#include <bits/stdc++.h>
using namespace std;

#define int long long

const int INF = 1e15;

struct edge{
    int u,v,c,d;
};

edge edges[50001];
set<pair<int,int>> adj[201];
bool visited[50001];
int dist[201][201];
int n;

int dijkastra(){
    priority_queue<pair<int,int>> q;
    for(bool&i:visited)i=false;
    int ans1 = INF;
    q.emplace(0,1);
    while(!q.empty()){
        auto curr = q.top();q.pop();curr.first=-curr.first;
        if(visited[curr.second])continue;
        visited[curr.second]=true;
        if(curr.second==n){ans1=curr.first;break;}
        for(auto&i:adj[curr.second]){
            if(!visited[i.first])q.emplace(-curr.first-i.second,i.first);
        }
    }
    while(!q.empty())q.pop();
    for(bool&i:visited)i=false;
    int ans2 = INF;
    q.emplace(0,n);
    while(!q.empty()){
        auto curr = q.top();q.pop();curr.first=-curr.first;
        if(visited[curr.second])continue;
        visited[curr.second]=true;
        if(curr.second==1){ans2=curr.first;break;}
        for(auto&i:adj[curr.second]){
            if(!visited[i.first])q.emplace(-curr.first-i.second,i.first);
        }
    }
    return ans1+ans2;
}

int32_t main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int m;
    cin >> n >> m;
    for(auto&i:dist)for(int&j:i)j=INF;
    for(int i=1;i<=m;i++){
        int u,v,c,d;
        cin >> u >> v >> c >> d;
        edges[i] = {u,v,c,d};
        adj[u].insert(make_pair(edges[i].v,edges[i].c));
        dist[u][v]=min(dist[u][v],c);
    }
    for(int i=1;i<=n;i++)dist[i][i]=0;
    for(int k=1;k<=n;k++){
        for(int i=1;i<=n;i++){
            for(int j=1;j<=n;j++){
                dist[i][j]=min(dist[i][j],dist[i][k]+dist[k][j]);
            }
        }
    }
    int baseans = dist[1][n]+dist[n][1];
    for(int i=1;i<=m;i++){
        int to = min(dist[1][n],dist[1][edges[i].v]+dist[edges[i].u][n]+edges[i].c);
        int back = min(dist[n][1],dist[n][edges[i].v]+dist[edges[i].u][1]+edges[i].c);
        if(to+back+edges[i].d<baseans){
            adj[edges[i].u].erase(adj[edges[i].u].find(make_pair(edges[i].v,edges[i].c)));
            adj[edges[i].v].insert(make_pair(edges[i].u,edges[i].c));
            baseans = min(baseans,edges[i].d+dijkastra());
            adj[edges[i].v].erase(adj[edges[i].v].find(make_pair(edges[i].u,edges[i].c)));
            adj[edges[i].u].insert(make_pair(edges[i].v,edges[i].c));
        }
    }
    cout << (baseans>=INF ? -1 : baseans) << '\n';
}

• Subtask 1: 5 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63