Submission #749132

#	Time	Username	Problem	Language	Result	Execution time	Memory
749132		onebit1024	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	371 ms	35536 KiB

commuter_pass

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

#define int long long
#define pb push_back
#define all(c) c.begin(), c.end()
#define endl "\n"

const double PI=3.141592653589;


void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define dbg(x...) cerr << "LINE(" << __LINE__ << ") -> " <<"[" << #x << "] = ["; _print(x)
#else
#define dbg(x...)
#endif

int n,m;
vector<vector<int>>nadj;
vector<vector<pair<int,int>>>adj;
int res;
vector<int> dij(int s){
    vector<int>dist(n+1,1e18);
    dist[s] = 0;
    priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>>pq;
    pq.push({0,s});
    while(!pq.empty()){
        int d = pq.top().first, u = pq.top().second;
        pq.pop();
        if(dist[u]!=d)continue;
        for(auto &[v,c] : adj[u]){
            int cur_dist = dist[v], new_dist = dist[u]+c;
            if(new_dist < cur_dist){
                dist[v] = new_dist;
                pq.push({new_dist, v});
            }
        }
    }
    return dist;
}

vector<int>dists,distt,distu,distv;


void solve()
{
    cin >> n >> m;
    adj.resize(n+1);
    nadj.resize(n+1);

    int s,t,u,v;
    cin >> s >> t >> u >> v;
    for(int i = 1;i<=m;++i){
        int u,v,c;
        cin >> u >> v >> c;
        adj[u].pb({v,c});
        adj[v].pb({u,c});
        
    }
    dists = dij(s);
    distt = dij(t);
    distu = dij(u);
    distv = dij(v);
    vector<int>deg(n+1),deg2(n+1);
    vector<vector<int>>rev(n+1);
    for(int i =1;i<=n;++i){
        for(auto &[v,c] : adj[i]){
            // check if edge i->v (directed) lies on shortest path from s->t
            if(dists[i]+c+distt[v] == dists[t]){
                nadj[i].pb(v);
                rev[v].pb(i);
                deg2[i]++;
                deg[v]++;
            }
        }
    }
    res = distu[v];
    queue<int>q;
    q.push(s);
    vector<int>vis(n+1),dp1(n+1),dp2(n+1);
    // dp1[i] min distance from v uptill node i for all nodes uptill i
    for(int i = 1;i<=n;++i){
        dp1[i] = dp2[i] = distv[i];
    }
    while(!q.empty()){
        int u = q.front();
        q.pop();
        if(vis[u])continue;
        vis[u] = 1;
        for(int v : nadj[u]){
            deg[v]--;
            dp1[v] = min(dp1[v],dp1[u]);
            if(deg[v]==0)q.push(v);
        }
    }
    q.push(t);
    vis = vector<int>(n+1);
    while(!q.empty()){
        int u = q.front();
        q.pop();
        if(vis[u])continue;
        vis[u] = 1;
        for(int v : rev[u]){
            deg2[v]--;
            dp2[v] = min(dp2[v],dp2[u]);
            if(deg2[v]==0)q.push(v);
        }
    }    

    for(int i = 1;i<=n;++i){
        if(vis[i])res = min(res, distu[i]+min(dp1[i],dp2[i]));

    }
    cout << res << endl;
}   

int32_t main()
{

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);


    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    

    int T=1;
    for(int i = 1;i<=T;++i)
    {
        // cout << "Case #" << i << ": ";
        solve();
    }
}

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