Submission #1063081

#	Time	Username	Problem	Language	Result	Execution time	Memory
1063081		_8_8_	Olympic Bus (JOI20_ho_t4)	C++17	5 / 100	1049 ms	8224 KiB

ho_t4

#include <bits/stdc++.h>

using namespace std;
    
typedef long long ll;
const int  N = 1e5 + 12, MOD = (int)1e9 + 7;
#define int ll
const ll inf = 1e16;
int n,m;
int U[N],V[N],C[N],D[N];
void dijkstra(int ver,vector<ll> &d,vector<int> &pr) {
    d.resize(n);
    pr.resize(n);
    for(int i = 0;i < n;i++) {
        d[i] = inf;
    }
    d[ver] = 0;
    vector<int> vis(n,0);
    vector<vector<int>> g;g.resize(n);
    for(int i = 0;i < m;++i) {
        g[U[i]].push_back(i);
    }
    for(int i = 0;i < n;i++) {
        int v = -1;
        for(int j = 0;j < n;j++) {
            if(vis[j]) continue;
            if(v == -1 || d[j] < d[v]) {
                v = j;
            }
        }
        vis[v] = 1;
        for(int t:g[v]) {
            int to = V[t],w = C[t];
            if(d[to] > d[v] + w) {
                d[to] = d[v] + w;
                pr[to] = t;
            }
        }
    }
}
vector<ll> d[N];
vector<int> p[N];
ll res = inf;
bool in[N];
void test() {
    cin >> n >> m;
    for(int i = 0;i < m;i++) {
        cin >> U[i] >> V[i] >> C[i] >> D[i];
        U[i]--;V[i]--;
    }
    for(int i = 0;i < n;++i) {
        dijkstra(i,d[i],p[i]);
    }
    res = d[0][n-1] + d[n - 1][0];
    vector<ll> bfd;
    vector<int> bfp;
    // for(int j = 0;j < m;j++) {
    //     in[j] = 1;
    //     swap(V[j],U[j]);
    //     ll nv = D[j];
    //     dijkstra(0,bfd,bfp);
    //     nv += bfd[n - 1];
    //     dijkstra(n - 1,bfd,bfp);
    //     nv += bfd[0];
    //     res = min(res,nv);
    //     swap(V[j],U[j]);
    // }
    auto make = [&](int j){
       in[j] = 1;
        swap(V[j],U[j]);
        ll nv = D[j];
        dijkstra(0,bfd,bfp);
        nv += bfd[n - 1];
        dijkstra(n - 1,bfd,bfp);
        nv += bfd[0];
        res = min(res,nv);
        swap(V[j],U[j]);
    };
    for(int i = 0;i < n - 1;i++) {
        if(d[0][i] != inf && i != 0) {
            make(p[0][i]);
        }   
        if(d[n - 1][i] != inf && i != n - 1) {
            make(p[n - 1][i]);
        }
    }
    for(int j = 0;j < m;j++) {
        if(in[j]) continue;
        swap(V[j],U[j]);
        ll nv = D[j];
        dijkstra(0,bfd,bfp);
        nv += bfd[n - 1];
        dijkstra(n - 1,bfd,bfp);
        nv += bfd[0];
        res = min(res,nv);
        swap(V[j],U[j]);
    }
    if(res >= inf) res = -1;
    cout << res << '\n';
}
signed main() {
    ios_base::sync_with_stdio(false);cin.tie(0);
    int t = 1; 
    // cin >> t;
    while(t--) {
        test();
    }
}  

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